Speaker:
Abadi Prayitno
Indonesian Institute of Space and Aeronautics (LAPAN), Bandung, Indonesia
Speaker:
Aburjania George
Tbilisi State University, Tbilisi, Georgia
GENERATION, INTENSIFICATION AND SELF-ORGANIZATION OF INTERNAL-GRAVITY WAVE STRUCTURES IN THE EARTH’S IONOSPHERE WITH DIRECTIONAL WIND SHEAR
Authors: G.D. Aburjania + I. Vekua Institute of Applied Mathematics of Tbilisi State University
A study is made of the generation and subsequent linear and nonlinear evolution of internal-gravity wave (IGW) structures in the dissipative ionosphere in the presence of a nonuniform zonal wind (a sheared flow). The efficiency of the linear amplification of IGW structures in their interaction with a nonuniform zonal wind is analyzed. When there are sheared flows, the operators of linear problems are non-self-conjugate and the corresponding eigenfunctions are nonorthogonal, so the canonical modal approach is poorly suited for studying such motions and it is necessary to utilize the so-called nonmodal mathematical analysis. It is shown that, in the linear evolutionary stage, IGW efficiently extract energy from the sheared flow, thereby substantially increasing their amplitude and, accordingly, energy (by several orders). The criterion for instability of a sheared flow in an ionospheric medium is derived. As the shear instability develops and the perturbation amplitude grows, a nonlinear self-localization mechanism comes into play and the process ends with the self-organization of nonlinear, highly localized, solitary IG vortex structures. The system thus acquires a new degree of freedom, thereby providing a new way for the perturbation to evolve in a medium with a sheared flow. Depending on the shape of the sheared flow velocity profile, nonlinear structures can be either purely monopole vortices or vortex streets against the background of the zonal wind. The accumulation of such vortices can lead to a strongly turbulent state in an ionospheric medium.
Shear flow, nonlinear solitary vortex, nonmodal mathematical analysis
Speaker:
Arras Christina
GFZ Potsdam, Potsdam, Germany
CHARACTERISTICS OF SPORADIC E LAYERS DERIVED FROM GLOBAL GPS RADIO OCCULTATION MEASUREMENTS
Authors: 1 Arras, C., 2 Mukhtarov, P., 2 Pancheva, D., 3 Jacobi, Ch., 1 Wickert, J.
1 German Research Center for Geosciences GFZ, Section1.1 GPS/Galileo Earth Observation, Potsdam, Germany
2 Geophysical Institute, Sofia, Bulgaria
3 University of Leipzig, Institute for Meteorology, Leipzig, Germany
The GPS radio occultation (RO) technique is employed to study sporadic E (Es) layers on a global scale. Our data set is based on FORMOSAT-3/COSMIC radio occultations and comprises about 2200 globally distributed RO measurements per day. GPS RO signals are sensitive to strong vertical electron density gradients that are found in the presence of Es layers. Theses gradients cause strong fluctuations in the signal to noise ratio of the GPS L1 frequency which are attributed to Es in this study.
The GPS RO data are used to obtain a global picture of sporadic E occurrence and its variability. In this study we focus on the equatorial region (20°N – 20°S) where a four-peaked longitudinal structure of sporadic E occurrence was detected. It is widely accepted that Es formation is due to the wind shear mechanism when the ionised constituents of the E region interact with the lower thermospheric neutral wind field. The lower thermospheric neutral wind field in turn is strongly influenced by solar atmospheric tides. Thus, we expect that the identified longitudinal wave-4 structure in equatorial sporadic E occurrence can be attributed to tidal activity, in particular to the nonmigrating tides. To investigate the correlation between Es occurrence and tidal activity, we compare Es rates with tidal information received from the lower thermospheric temperature field that was measured by the SABER instrument on the TIMED satellite.
Ionosphere, Sporadic E, Tides, GPS radio occultation
Speaker:
Becker Erich
Leibniz Institute of Atmospheric Physics at the Rostock University, 18225 Kühlungsborn, Germany
SOME EXAMPLES FOR MODULATIONS OF THE WAVE DRIVING IN THE SUMMER MLT
Authors: 1 Becker, E., 1 R. Knöpfel, 1 N. Engler, 2 C. von Savigny, 1 Leibniz Institute of Atmospheric Physics, Kühlungsborn, Germany, 2 Institute of Environmental Physics, Unviversity of Bremen, Gemany
The summer-to-winter-pole residual circulation in the upper meosphere is driven by gravity waves. In the northern winter hemisphere the westward gravity-wave drag is strongly modulated by the variability of the polar vortex which in turn is controlled by quasi-stationary Rossby waves. An analogous modulation of the eastward gravity-wave drag in the summer mesopause region is not possible since quasi-stationary Rossby waves are filtered by the westward stratospheric jet in summer. Nevertheless, the gravity-wave drag in summer can be modulated by the polar vortex in winter through interhemispheric coupling. It is therefore likely that the gravity-wave driving in summer is also affected through other mechanisms.
In this contribution we focus on modulations of the gravity-wave driving that are induced by 1) solar proton events, 2) thermal tides, and 3) an altered radiation budget caused by increased CO2-concentrations. All model results are deduced from sensitivity experiments with the Kühlungsborn Mechanistic general Circulation Model (KMCM).
In the first two examples, the perturbations give rise to variations of the background wind that cause eastward gravity waves to attain shorter vertical wavelengths. This implies a downward shift of the equatorward branch of the residual circulation and hence an anomalous dynamical warming of the mesopause region.
In the third example, the overall radiative cooling in the middle atmosphere is reversed in the region of the cold summer mesopause, inducing an anomalous westward background wind component in response to CO2 doubling. In turn, the gravity wave drag maximum is shifted to higher altitudes, inducing a dynamic cooling which partly offsets the radiative perturbation. This mechanism should
be contrasted to the effect of enhanced tropospheric gravity-wave sources which may also be expected to arise from climate change and lead to a cooling of the polar summer mesosphere that peaks around the mesopause.
gravity waves, residual circulation, sensitivity experiments
Speaker:
Bessarab Fedor
WDIZMIRAN, Kaliningrad, Russia
MODELING OF THE EFFECT OF SUDDEN STRATOSPHERIC WARMING ON THE THERMOSPHERE-IONOSPHERE SYSTEM
Authors: E.g.,1 Korenkov Yu.N., 1 Karpov I.V.
1 Western Department of IZMIRAN, Kaliningrad
Poster presentation
The problem of relation between stratosphere and mesosphere and lower thermosphere (MLT) is of great scientific interest since it is connected with influence of the meteorological effects on the state of the ionosphere. It is known that sudden stratosphere warming (SSW) may be related with polar MLT cooling, by means of wave processes. The modeling results of the of the effects of stratospheric warming are presented in this study. The Global Thermosphere-Ionosphere-Protonosphere Model (GSM TIP) was used for the obtaining temporal variations thermosphere-ionosphere parameters. Results were obtained for the 80-520 km altitudes region, for the winter in the North hemisphere and quiet geomagnetic conditions. The effect of SSM was simulated by decreasing of the neutral temperature at the lower boundary. Spacial and temporal variations of the thermosphere and ionosphere parameters were studied. These results are compared with another experimental and theoretical data.
sudden stratosphere warming, thermosphere, ionosphere, modelling
Speaker:
Candido Claudia
INPE, Sao Jose dos Campos, Brazil
SOUTHERN ANOMALY CREST SPREAD-F IN JUNE SOLSTICE DURING THE SOLAR CYCLE 23
Authors: Candido, Claudia M. N.1, Batista, I. S.1, Becker-Guedes, F.1; Abdu, M. A.1, Sobral, J. H. A.1, Takahashi, H.1
1. National Institute for Space Research - INPE
Poster presentation
At Brazilian low latitudes, the spread-F as seen by ionosondes or imaging systems is mostly associated with equatorial plasma bubbles (EPBs), mainly between October and March. On the other hand, during low solar activity and the June solstice periods, the observation of EPBs at low latitude sites is very rare, presenting an occurrence about 11%. In this work we present a study of a series of spread-F events observed over the Southern anomaly crest (Cachoeira Paulista 22.7oS, 45.0 o W, mag lat: 16 o S, dip angle: -22.3o, Brazil) during last solar cycle, which presented an extended solar minimum period. After analyzing hundreds of ionograms obtained with a digital ionosonde DGS 256, between 2001 and 2010, we verified a high occurrence of Midnight-Post Midnight spread-F at June Solstice (South Winter) with a peak between 2006 and 2009, when the solar flux has reached very low values (< 70 SFU). The spread-F frequently present high intensities, despite the low plasma densities of the period (foF2 < 6 MHz) and can extends for several hours. We have found evidences that spread-F events can be caused by ionospheric disturbances as medium scale traveling ionospheric disturbances (MSTIDs) come from higher latitudes. Finally we present a statistical analysis of the events.
spread-F, solar minimum, low latitudes
Speaker:
Chargazia Khatuna
M. Nodia Institute of Geophysics, Tbilisi, Georgia
THE INTERACTION OF PLANETARY ROSSBY WAVE STRUCTURES WITH INHOMOGENEOUS GEOMAGNETIC FIELD AND SHEARED WIND IN THE UPPER ATMOSPHERE
Authors: 1 Kh. Z. Chargazia, 2 G.D. Aburjania, 1 M. Nodia Institute of Geophysics, Tbilisi, Georgia,
2 I. Vekua Institute of Applied Mathematics of Tbilisi State University
Interaction of inhomogeneous geomagnetic field with the planetary usually Rossby waves generates the magnetized Rossby-type wavy perturbations in the upper atmosphere and ionosphere. An effective linear mechanism responsible for the intensification and mutual transformation of large scale magnetized Rossby type and small scale inertial waves in the shear wind driven ionosphere is found. To study the interaction of shear flow (inhomogeneous wind) and wave structures in the atmosphere-ionosphere regions, more adequate is nonmodal mathematical analysis. Using nonmodal approach and numerical modeling, it is illustrated the peculiar features of the interaction of magnetized Rossby waves with the background flow as well as the mutual transformation of Rossby-inertial wave disturbances in the ionosphere. It has been shown that the shear flow driven magnetized Rossby wave perturbations effectively extract energy of the shear flow increasing own energy and amplitude. These perturbations undergo self organization in the form of the nonlinear solitary vortex structures due to nonlinear twisting of the perturbation’s front. Such nonlinear vortex structures are often observed in different regions of the atmosphere-ionosphere layers of the Earth.
Rossby type waves, shear flow, self-organisation into vortex structures
Speaker:
Cherniak Iurii
West Department of Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, Kaliningrad, Russia
THE ANALYSIS OF IONOSPHERIC MODIFICATIONS DURING MAY 2010 GEOMAGNETIC STORMS BY RADIOPHYSICAL MEASUREMENTS DATA
Authors: 1Cherniak, Iu.V., 1Shagimuratov, I.I., 1Korenkova, N.A., 1Leschenko, V.S. WD IZMIRAN
At the beginning of the new 24th solar cycle several geomagnetic storms were occurred. One of the most essential storms took place on May 2-3, 2010 and another one, the first geomagnetic storm with Dst index lower then -90 nT after extended solar minimum, was observed on May 29, 2010. The first storm has well pronounced positive phase before noon of 2 May, the second storm started before midnight. The ionosphere response on these events was analyzed by using the ionospheric sounding data.
The three ionosondes which formed a triangle in the mid-latitudes of the central European region were selected for the given analysis. There are the “Parus” ionosonde at the observatory of the West Department of IZMIRAN (Kaliningrad, Russia) and two digisondes located in Pruhonice (Czech Republic) and Juliusruh (Germany). Also at Kaliningrad observatory variations of geomagnetic field were registered. The digisonde data were provided by the DIAS network. The ionograms derived from all ionosondes were scaled manually in order to exclude errors related with autoscaling. For comparative analysis were calculated median values for non-disturbed days of May 2010.
For detailed analysis of height ionosphere structure modification we combined ionosonde derived data with the GPS COSMIC radio occultation electron density profiles. For analysis are used occultations located inside triangle formed by ionosondes.
The peak electron density (foF2) variations and shape of the electron density profiles were analyzed. The differences of ionosphere responses to May 2010 geomagnetic storms were studied. The time and quantitative characteristics of the ionosphere modifications during May 2010 geomagnetic storms were revealed.
ionosphere, geomagnetic storm, ionosonde,
Speaker:
Chum Jaroslav
Institute of Atmospheric Physics, Czech Republic, Prague, Prague, Czech Republic
ON THE SEASONAL VARIATION OF HORIZONTAL PROPAGATION OF GRAVITY WAVES IN THE IONOSPHERE
Authors: Chum, J. (1), J. Baše (1), D. Burešová (1), F. Hruška (1) , J. Laštovička (1), T. Šindelářová (1)
L. A. McKinnell (2), R. Athieno (2)
Using a multi-point Continuous Doppler sounding system we investigate propagation directions and velocities of Gravity Waves (GWs) in the ionosphere at altitudes from ~150 km to ~250 km. The velocities and directions are computed from the time delays between the observations of corresponding GWs at different reflection points that correspond to various sounding paths. We focused on the GWs that produce an S-shaped trace in Doppler shift spectrograms since it is know that these patterns are formed if the disturbances (waves) mainly propagate in the horizontal plane. The S-shaped signatures also make it possible to estimate the errors of measurements.
The system that we used was developed in the Institute of Atmospheric Physics, Czech Republic and has been operated in the western part of the Czech Republic. A similar system was also installed in the Western Cape, South Africa at the end of May 2010.
A statistical study shows that the analyzed GWs propagate with typical horizontal velocities from ~100 to ~200 m/s. The north-south component of GW velocities depends on the season and/or daytime. The analyzed waves propagated northward from April to August. At the same time, the north-south component of neutral winds calculated by the HWM07 model had an opposite sign.
ionosphere, gravity waves
Speaker:
Day Kerry
The University Bath , Bath, United Kingdom
Speaker:
England Scott
University of California Berkeley, Berkeley, United States
MODELING IONOSPHERIC ELECTRODYNAMIC EFFECTS OF TIDES
Authors: S.L. England, Space Sciences Laboratory, University of California Berkeley
A number of recent studies have highlighted the observational evidence for a communication between atmospheric tides in the thermosphere and the electron density structure of the ionosphere. The most commonly proposed mechanism to explain this is an electrodynamic coupling between tides at E-region altitudes and ion drifts at F-region altitudes. However, based on both the observational evidence from recent satellite missions and considering the theoretical effects of atmospheric tides on the thermosphere and ionosphere, more than one coupling mechanism must be considered. Results from the NRL-SAMI2 model will be shown that test a set of electrodynamic and chemical-dynamical coupling mechanisms that could explain the link between tides in the thermosphere and the low-latitude ionosphere. These results indicate that more than one of these mechanisms are plausible, given current observational constraints. The results of this work will be presented with a focus on what future modeling and observational efforts will be required in order to eliminate or verify the proposed coupling mechanisms.
Tides, ionosphere, electrodynamics
Speaker:
Fritts Dave
NorthWest Research Associates/CoRA, Boulder, United States
QUASI-LINEAR AND NONLINEAR DYNAMICS OF GRAVITY WAVES IN THE THERMOSPHERE AND POTENTIAL PLASMA RESPONSES
Authors: Dave Fritts and Tom Lund, NWRA/CoRA, Boulder CO
This talk will describe recent numerical studies of large-scale and large-amplitude gravity wave propagation and nonlinear behavior in deep domains. Important neutral atmosphere effects include strong tidal interactions and filtering, induced mean flows, large-scale turbulence, and mixing. We also consider the implications of these dynamics for gravity wave influences on plasma dynamics occurring at comparable spatial scales.
gravity waves, instabilities and turbulence, thermosphere, ionosphere, plasma dynammics
Speaker:
Fukushima Daisuke
Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan
STUDY OF EQUATORIAL MEDIUM-SCALE TRAVELLING IONOSPHERIC DISTURBANCES IN 630-NM AIRGLOW IMAGES
Authors: 1 Daisuke Fukushima,1 Kazuo Shiokawa,1 Yuichi Otsuka, 2 Tadahiko Ogawa, 1 Solar-Terrestrial Environment Laboratory, Nagoya University, Japan, 2 National Institute of Information and Communications Technology, Japan
Poster presentation
We study nighttime medium-scale travelling ionospheric disturbances (MSTIDs) observed at Kototabang (0.2S, 100.3E, geomagnetic latitude : 10.6S), Indonesia during 7 years from 26 October 2002 to 25 October 2009. The MSTIDs were observed in 630-nm night airglow images which were taken with exposure times of 105-165 s and time resolutions of 4.5-5.5 min by using a highly-sensitive all-sky airglow imager. The average and standard deviation of the horizontal phase velocity and period of the MSTIDs were 316.7, 166.0 m/s and 42.1, 10.5 min, respectively. The previous study suggested that acoustic gravity waves in the thermosphere caused the observed MSTIDs, because the observed MSTIDs mostly had east-west phase fronts. In this observation during 7 years from solar maximum to minimum, the airglow emission became weaker and the observation rate of MSTIDs decreased year by year. This fact may suggest that the gravity waves are difficult to propagate when the solar activity is weaker because neutral viscosity in the thermosphere increases for decreasing solar activities. However the decrease of the signal-to-noise ratio and the decline of the imager sensitivity may also affect this positive correlation. We also found positive correlation between the propagation directions of the observed MSTIDs and the location of tropospheric convection activity identified by hourly maps of equivalent black body temperature (TBB). The propagation directions of MSTIDs were usually southward or southwestward and they were most frequently observed between May and July when intertropical convergence zone (ITCZ) locates north of Kototabang. These facts suggest that acoustic gravity waves generated in the troposphere are one of the source of observed MSTIDs.
MSTID, equatorial thermosphere, nighttime airglow
Speaker:
Galav Praveen
M L S University, Udaipur, Udaipur, India
THE EQUATORIAL AND LOW LATITUDE IONOSPHERIC RESPONSE TO THE SPACE WEATHER DISTURBED WEEK OF NOVEMBER 2004 - A CASE STUDY
Authors: P. Galav, Shweta Sharma and R. Pandey
Department of Physics
Mohanlal Sukhadia University
Udaipur, INDIA
Poster presentation
The Global positioning system derived TEC provides the information about the variations of the ionosphere during quiet as well as geomagnetically disturbed conditions. In the present study we have analyzed the GPS-TEC data for three Indian GPS stations (covering the region from magnetic equator to 20º N magnetic latitude) for the Space weather disturb week of November 2004. The suppression in the low latitude Total Electron Content on November 8 and November 10 can be attributed to the disturbance dynamo electric field whereas the anomalous enhancement in low latitude TEC on November 9 is the result of prompt penetration electric field. Observation of TEC enhancement on November 11, after ~48 hours of southward turning of the Interplanetary magnetic field (IMF Bz) on November 9, 2004 indicate a positive phase of geomagnetic storm. Some new results on the effect of prompt penetration and disturbance dynamo electric field on the ionospheric TEC would be presented and discussed during the workshop.
Space weather, EIA, GPS-TEC, Geomagmetic storm
Speaker:
Georgieva Katya
Space and Solar-Terrestrial Research Institute, Sofia, Bulgaria
Speaker:
Grygalashvyly Mykhaylo
Leibniz-Institute of Atmospheric Physics, Kuehlungsborn, Germany
WAVE-MIXING EFFECTS ON MINOR CHEMICAL CONSTITUENTS IN THE MLT-REGION
Authors: Grygalashvyly M., Becker E., Sonnemann G. R.
IAP, Leibniz-Institute of Atmospheric Physics, Kühlungsborn, Germany
We study the influence of gravity waves (GWs) on the distributions of minor chemical constituents in the mesosphere/lower thermosphere (MLT) on the basis of a 3-dimensional global chemistry-transport model called MECTM. The MECTM is driven by the dynamics of the Kuehlungsborn Mechanistic general Circulation Model (KMCM) which resolves mid-frequency GWs down to horizontal wave lengths of 350 km and describes their wave-mean flow interaction is a self-consistently by means of an advanced turbulent diffusion scheme. The effects of GWs on the transport and photo chemistry of minor constituents is assessed on the basis of a sensitivity experiment. In our control simulation, the MECTM is driven with the full dynamical fields from an annual cycle simulation with the KMCM, A perturbation simulation with just the MECTM is defined by eliminating all mesoscale variations with horizontal wavelengths shorter than 1000 km from the dynamical fields via spectral filtering. Hence, both MECTM-simulations are driven by the same large-scale dynamics. For reasons of consistency, we also apply the same numerical grid and time step in these simulations. The response of the MECTM to GW perturbations reveals strong effects on the trace-gas concentrations. In particular, constituents with large photochemical lifetime are strongly affected by vertical wave mixing, while constituents with short lifetime reflect the dependence of their reaction rates on mesoscale temperature perturbations and on the changed distribution of long-living constituents. The mean model response varies with latitude and season, but is strongest around the mesopause where also the GW amplitudes are largest. We present detailed discussions of the simulated GW effects on water vapor, atomic oxygen, carbon dioxide, and odd hydrogen and we highlight the consequences for our understanding of the general circulation of the MLT.
gravity waves, chemistry of atmosphere, MLT, modelling, atmosphere
Speaker:
Gurubaran Subramanian
Indian Institute of Geomagnetism, Tirunelveli, India
TIDAL STRUCTURES IN THE EQUATORIAL IONOSPHERE: COUPLING
BETWEEN THE LOW-ALTITUDE THERMOSPHERE AND HIGH-ALTITUDE IONOSPHERE
Authors: 1 S. Gurubaran, 1 R. Dhanya, 1 K. Ajith Kumar, 2 S. Sridharan, 3 T. Tsuda, 4 H. Takahashi, 4 P. P. Batista, 4 B. R. Clemesha, 5 R. A. Buriti, 6 D. V. Pancheva and 7 N. J. Mitchell,
1 Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli, India,
2 National Atmospheric Research Laboratory, Tirupati, India,
3 Research Institute of Sustainable Humanosphere, Kyoto University, Kyoto, Japan,
4 Instituto Nacional de Pesuisas Espaciais, Sao Jose dos Campos, Brazil,
5 Departmento de Fisica, Universidade Federal de Campina Grande, Campina Grande, Brazil, 6 Geophysical Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria,
7 Centre for Space Atmospheric and Oceanic Science, Department of Electronic and Electrical Engineering, University of Bath, Bath, UK
Planetary-scale waves like tides, global-scale normal modes and equatorial Kelvin waves play an important role in the dynamics of the mesosphere-lower thermosphere (MLT) region. It has been hypothesized in the past that if a global-scale wave with large amplitude and fairly long vertical wavelength propagates into the ionosphere from below, it should drive an electric current system through the dynamo action with a period of the global-scale wave. This wave-like perturbation causes perturbations in geomagnetic field that could be recorded on ground. Part of these variabilities during magnetically quiet times could very well be due to the variabilities of tides and other planetary-scale waves but what conditions exist in the MLT region that permit these large-scale waves to reach the dynamo heights and have an influence on the ionospheric variabilities there and higher above are not known. Aiming to resolve this issue, we performed an analysis of simultaneous observations of MLT winds from four longitudinally separated sites, Tirunelveli (8.7 N, 77.8 E), Pameungpeuk (7.7S. 107.7E), Ascension Island (7.9 S, 14.4 W) and Cariri (7.4 S, 36.5 W) with the objective of delineating the role of tides and planetary waves in driving the short-term (day-to-day to few days) variabilities of ionospheric current systems at low latitudes. Results from this exercise will be presented and discussed in the current context of our understanding of this coupling between the MLT region and the E-region ionosphere at low latitudes.
Tides, Planetary waves, Ionospheric current system
Speaker:
Haeusler Kathrin
GFZ German Research Centre for Geosciences, Potsdam, Germany
THE TROPOSPHERIC INFLUENCE ON THE EQUATORIAL ELECTROJET AND THE UPPER THERMOSPHERIC ZONAL WIND AS OBSERVED BY CHAMP
Authors: 1 Haeusler, K., 1 Luehr, H., 2 Oberheide, J., 3 Maus, S., 1 GFZ German Research Centre for Geosciences, Potsdam, Germany, 2 Dept. of Physics and Astronomy, Clemson University, Clemson, SC, USA, 3 CIRES, University of Colorado, Boulder, CO, USA
The equatorial electrojet (EEJ) as well as the upper thermospheric zonal wind derived from CHAMP measurements exhibit a 4-peaked longitudinal structure that can be attributed to the eastward propagating diurnal tide with zonal wavenumber 3 (DE3). The former one is observed at 105 km altitude, the latter one at 400 km altitude. Yet both quantities exhibit the same DE3 inter-annual variation with a two year peak-amplitude modulation. Interestingly, DE3 is excited in the tropical troposphere in deep convective clouds and its influence on upper atmospheric parameters was not anticipated before. In this study we're going to present the CHAMP observed DE3 amplitudes in the EEJ and zonal wind and compare it to the DE3 zonal wind amplitudes in the mesosophere lower thermosphere and at 400 km altitude calculated with a physics-based empirical model based on Hough Mode Extension fits to TIMED tides. Further attention will be given to other nonmigrating tides such as the eastward propagating diurnal tide with zonal wavenumber 2 (DE2).
nonmigrating tides, ionosphere, thermosphere, CHAMP
Speaker:
Hoffmann Peter
Leibniz-Institute of Atmospheric Physics Kühlungsborn, 18225 Kühlungsborn, Germany
CHANGES OF THE TIDAL ACTIVITY IN THE MLT REGION DURING AND AFTER SUDDEN STRATOSPHERIC WARMING (SSW) EVENTS
Authors: Hoffmann, P., Goncharenko, L. P., Hocke, K., Matthias, V. Rapp, M., Singer W., Miller A. , Schmidt, H., Zülicke, Ch.,and Straub, C.
Recent studies show in connection with SSWs an enhancement of tidal waves that are considered as key processes for influences of changes in the ionosphere.
These enhancements are not really understood. To answer the question: What causes the enhancement of tidal activity in the MLT region after SSW, we will investigate the temporal development of planetary, tidal and gravity waves in connection with SSW based on long-term observations with MF - and Meteor radar observations in Andenes (69°N, 16°E) since 1999 at polar latitudes and in Juliusruh (55°N, 13° E) since 1990 at middle latitudes. For case studies, the altitudinal dependence of long period waves with periods of 8 - 20 days that are present throughout the atmosphere and may induce SSWs, are additionally investigated by temperatures derived from the MLS experiment on board of the AURA satellite and by ozone and water vapor variations in the upper stratosphere/ lower mesosphere derived from microwave observations in Bern (47°N, 8°E) and Sodankylä (67°N, 26°E). The interpretation of the observational diagnostics is provided by complementary modeling efforts.
sudden stratospheric warming events, tidal waves, planetary waves, gravity waves
VERTICAL COUPLING PROCESSES DUE TO WINDS AND WAVES OVER AN EXTENDED ALTITUDE RANGE (ISSI TEAM)
Authors: Hoffmann, P. and the ISSI team:
K. Hocke, S. Nozawa, L. P. Goncharenko, H. Schmidt, A. Miller, Ch. Zülicke, C. Straub, E. DeWachter, R. Rüfenacht, J. Oberheide, I. Häggström
The presentation gives an overview about interdisciplinary studies of the ISSI team 152: Bridging the gap between the middle and upper atmosphere: Coupling processes due to winds and waves over an extended altitude range.
The International Space Science Institute (ISSI) at Bern (Switzerland) acts as a catalysator for scientists and experts from all over the world who like to combine their theoretical, experimental, observational, intuitive and analytical skills for solving open problems in Earth system and space science.
A well-known observational lack exists in remote sensing of neutral winds of the lower mesosphere and lower thermosphere where strong wind jets appear. Neutral wind retrieval from incoherent scatter (IS) radar data can partly remove this shortcoming. Using wind observations with MF-, Meteor- and IS radars at polar and middle latitudes together with long period variations of ozone and water vapor in the upper stratosphere/ lower mesosphere derived from microwave observations, the main project activities are concentrated on concrete case studies about dynamical coupling processes from the stratosphere up to the lower thermosphere
a) during sudden stratospheric warming events and to investigate possible coupling processes between different layers with spatial emphasis on the influence on the ionosphere, and on
b) temporal development of wind reversals and their influence on waves and temperature up to thermospheric heights during fall transition.
The interpretation of the observational diagnostics and the elucidation of the impact of the associated processes on the MLT are provided by complementary modeling efforts and by the additional evaluation of global satellite data.
middle atmosphere dynamics, tides, stratospheric warming
Speaker:
huang cheryl
Air Force Research Laboratory, Hanscom AFB, MA 01731, United States
TIDAL STRUCTURES IN THE EQUATORIAL IONOSPHERE
Authors: 1C. Y. Huang, 2S. H. Delay, 1P. A. Roddy and 1E. Sutton
1 Space Vehicles Directorate, AFRL
2 Institute for Scientific Research, Boston College
Tidal structures have been noted at altitudes up to 840 km in both neutrals and ions. We present examples of simultaneous ion and neutral tidal structures obtained by the Plasma Langmuir Probe on C/NOFS and the SuperStar accelerometer on GRACE. Under the very quiet conditions during solar minimum, the tidal features are very distinct. Climatology of the tidal structures on C/NOFS is similar to that of planetary waves which are presumably the source of the high-altitude observations. The ion and neutral tidal structures are decoupled, however both exhibit a large density decrease on the nightside around 330 degrees longitude. We will discuss possible mechanisms for the creation of this structure.
equatorial ionosphere, tidal structures
Speaker:
Kanukhina Anna
Russian State Hydrometeorological University, St.Petersburg, Russia
INFLUENCE OF THE QBO, NAM AND ENSO ON PLANETARY WAVE-DRIVEN INTERANNUAL VARIABILITY OF THE SPRING TRANSITION
Authors: Anna Kanukhina1, Elena Savenkova1, Evgeniy Merzlyakov2, Alexander Pogoreltsev1
1- Russian State Hydrometeorological University, St. Petersburg, Russia
2- Institute for Experimental Meteorology, RPA
The analysis of data assimilated in the UK Met Office and NCEP models shows that there exists a sufficiently strong (in the range of about two months) interannual variability of the spring-time breakup date of stratospheric circulation. The preliminary results show also that spring-time transition depends on the planetary-wave activity in the stratosphere and during the last decades there is a tendency of the shift of the breakup to the later date. The main purpose of the present paper is to investigate the possible reasons of observed interannual variability of the spring-time breakup date. Increase of the amplitude of stationary planetary wave with zonal wave number 1 (SPW1) observed during the last decades in February leads to a substantial decrease of the SPW1 amplitude in March that can explain the observed shift to the later spring-time breakup date. Scatter plot between NAM and the spring-time breakup date shows a positive correlation, which is stronger for the early spring-time transition. Under east-QBO taken at 40-50 hPa according to the established classification, growth of the SPW1 amplitude is accompanied with the early spring-time transition. Under west-QBO conditions the correlation between the SPW1 amplitude and the date of spring-time transition is positive. Statistically significant positive correlation between MEI index of ENSO and spring-time breakup has been obtained under east-QBO conditions. This means that cold ENSO leads to early occurrence of spring-time transition in spite of the stronger polar vortex.
Speaker:
Karpov Ivan
West department of N.V. Pushkov IZMIRAN RAS, Russia, Kaliningrad, Russia
PLANETARY WAVE DISTURBANCES IN THE MIDLATITUDE IONOSPHERE DURING GEOMAGNETIC STORMS
Authors: Karpov I.V., Shagimuratov I.I., Yakimova, G.A., Suslova O.P.
WD IZMIRAN, Kaliningrad, Russia
Poster presentation
Analysis of the diurnal variations of TEC (Total Electron Content) at midlatitude stations showed that in periods of geomagnetic disturbances and after them marked strengthening of the ionosphere variations with periods of 4-8 hours. Such perturbations can persist for several days after the storm. The analysis of perturbations of the diurnal TEC variations at midlatitude stations shows that the spectrum of TEC perturbations are determined by amplification of harmonics with periods of 4-5 h and 6-8 h. The periods such perturbations increasing with decreasing latitude. The slow variations of ionosphere(τ = 6-8 hours) have high sensitivity to the geomagnetic disturbances. It is suggested that observed disturbances of TEC variations are caused by the excitation of planetary Poincare waves in the atmosphere. Latitudinal dependences of the periods and amplitudes of the spectral harmonics have consistent with the dispersion relations for Poincare waves with zonal wavenumbers s = 1, 2 and meridional wavenumbers n = 1, 2 with a width of atmosphere channel L ~ 12000 km. The possibilities of forming such atmosphere channel and generation of Poincare waves during geomagnetic disturbances is discussed.
ionosphere, TEC, planetary Poincare waves
Speaker:
Kherani Esfhan Alam
Instituto nacional de pesquisais espaciais, Sao Jose Dos Campos, Brazil
THE EFFECTS OF THE ACOUSTIC-GRAVITY WAVES IN THE GENERATION AND SUPPRESSION OF PLASMA BUBBLES IN THE EQUATOR-LOW-LATITUDE IONOSPHERE
Authors: E.A. Kherani, M. Matheus, M.A. Abdu, E.R.de Paula and J.H.A. Sobral, Instituto Nacional de Pesquisais Espaciais, Brazil
Poster presentation
In this work, we will present the varieties of effects of the tropospheric-generated acoustic-gravity-waves (AGWs) in the generation and suppression of plasma bubbles. Using three-dimensional coupled simulation model of AGW-plasma bubble, it will be shown that AGW is a possible candidate for the seeding of collisional-interchange instability (CII). It provides the wind perpendicular to the Earthś magnetic field that has strong vertical shear. Such wind and associated shear may efficiently excite the CII and plasma bubble. On the other hand, AGW also provides wind parallel to Earthś magnetic field that may act to suppress the CII and plasma bubble. The competing role of wind components associated with AGWs to excite and suppress the plasma bubble will be examined in this work.
gravity wave, plasma bubble
Speaker:
Klimenko Maxim
WD IZMIRAN, Kaliningrad, Russia
THE FORMATION MECHANISM OF THE F3-LAYER AND ITS BEHAVIOR DURING GEOMAGNETIC STORMS
Authors: 1,2 Klimenko M.V., 1 Klimenko V.V., 3 Karpachev A.T., 4 Ratovsky K.G. 1 West Department of N.V. Pushkov IZMIRAN RAS, Kaliningrad, Russia, 2 Kaliningrad State Technical University, Kaliningrad, Russia, 3 N.V. Pushkov IZMIRAN RAS, Moscow, Russia, 4 Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia
The huge number of researches is devoted to formation of additional layers in F-region of equatorial ionosphere, first of which has been published more 60 years ago. Originally the occurrence of such layers has received the name “stratification of equatorial F2-layer”. However, in the middle of 90-s' years of the last century it has been shown, that the additional maximum above F2-layer maximum in the equatorial ionosphere exists regular enough and at the certain Local Time. From this point onwards it was named by F3-layer, and instead of the term “stratification of equatorial F2-layer” the most of researches began to speak about formation of the F3-layer. The theoretical and experimental researches which have been carried out last 20 years, have shown, that the F3-layer is formed by zonal component of electric field with assistance of meridional component of thermospheric wind. However, it is necessary to notice, that till now there is no precisely formulated physical mechanism of F3-layer formation. The given research is devoted to detailed investigation of the formation mechanism of F3-layer in quiet geomagnetic conditions and its variations during geomagnetic disturbances. These researches are based on calculation results obtained with use of the model GSM TIP and experimental data of Interkosmos-19 satellite and digital ionosondes.
The research is carried out at financial support of the Russian Foundation for Basic Research (Grant №08-05-00274).
equatorial ionosphere, F3-layer, numerical modeling, geomagnetic storms
BEHAVIOR OF EXTERNAL IONOSPHERE PARAMETERS DURING GEOMAGNETIC STORM SEQUENCE ON SEPTEMBER 9-14, 2005
Authors: 1,2 Klimenko M.V., 1 Klimenko V.V., 3 Truhlik V. 1 West Department of N.V. Pushkov IZMIRAN RAS, Kaliningrad, Russia,
2 Kaliningrad State Technical University, Kaliningrad, Russia, 3 Institute of Atmospheric Physics, ASCR, Prague, Czech Republic
Earlier we have carried out the researches of behavior of ionosphere F-region parameters during geomagnetic storm sequence on September 9-14, 2005. These researches have been executed with use of the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) and experimental data of digital ionosondes, incoherent scatter radars and GPS receivers. The comparison of ionospheric effects of geomagnetic storms obtained in modeling calculations, with experimental data has revealed the satisfactory agreement. In the given work the results of researches of this storm sequence effects in the external ionosphere are presented. The comparison of calculation results of electron concentration and electron temperature with experimental data of DMSP F13 and F15 satellites (height of ~830 km) is carried out. Besides on the basis of model calculation results the global maps of disturbances of various parameters of the external ionosphere during geomagnetic storms are constructed and physical interpretation of the obtained effects is submitted.
The research is carried out at financial support of the Russian Foundation for Basic Research (Grant №08-05-00274).
geomagnetic storm, external ionosphere, numerical modeling, DMSP data
Speaker:
Klimenko Vladimir
West department of N.V. Pushkov IZMIRAN RAS, Kaliningrad, Russia
RESEARCH OF THE ROLE OF DISTURBED IONOSPHERIC DYNAMO ELECTRIC FIELD IN BEHAVIOR OF MID- AND LOW-LATITUDE IONOSPHERE PARAMETERS DURING GEOMAGNETIC STORM
Authors: 1 Klimenko V.V., 1,2 Klimenko M.V., 1 West Department of N.V. Pushkov IZMIRAN RAS, Kaliningrad, Russia, 2 Kaliningrad State Technical University, Kaliningrad, Russia
The essential role of the disturbed ionospheric dynamo electric field in behavior of the ionosphere during geomagnetic disturbances was marked by many researchers. However till now it has not been carried out the researches of disturbed ionospheric dynamo electric field generated by variations of magnetosphere convection electric field and electric field of Alfven layer connected with field aligned currents of the second region, during geomagnetic storm at various phases of its development. In the given research we represent the results of modeling calculations of the disturbed dynamo electric field and its ionospheric effects at middle and low latitudes for geomagnetic storm on December 14-15, 2006. Calculations have been executed with use of the Global Self-consistent Model of Thermosphere, Ionosphere and Protonosphere (GSM TIP), developed in West department of IZMIRAN. At that the dependence of potential difference through polar caps and field-aligned currents of the second region from AE-index of geomagnetic activity with the one-minute resolution and high-energy particle precipitation dependent on 3-hour Kp-index of geomagnetic activity was taken into account. Besides it was taken into account half-hour delay of development of the second region field-aligned currents relative to the variations of potential difference through polar caps and their shift to equator with growth of geomagnetic activity. Calculations were carried out for quiet and disturbed conditions with took into account the superposition of dynamo electric field and magnetosphere convection electric field, and also without taking into account dynamo field. It has allowed separating off the effects of the disturbed dynamo electric field in parameters of the ionosphere and thermosphere. It was carried out the analysis of obtained calculation results and it was drawn the conclusion about the role of the disturbed dynamo electric field in the ionosphere during geomagnetic disturbances.
The research is carried out at financial support of the Russian Foundation for Basic Research (Grant №08-05-00274).
geomagnetic storm, disturbed dynamo electric field, numerical modeling
Speaker:
Knöpfel Rahel
Leibniz Institut of Atmospheric Physics, Germany, Kühlungsborn, Germany
A NEW CONTINUOUS RADIATIVE TRANSFER SCHEME TO STUDY COUPLING PROCESSES FROM THE SURFACE UP TO THE MESOPAUSE REGION
Authors: 1 Knöpfel R., 1 Becker E., 1 Leibniz-Institut of Atmospheric Physics e.V. at the University Rostock, Kühlungsborn
A simplified and numerically efficient method to compute radiative flux densities and heating rates in a general circulation model (GCM) is presented. The parameterization extends continuously from the surface up to the lower thermosphere and avoids any merging of radiative heating rates from different schemes, which is usual in comprehensive middle atmosphere GCMs. To investigate coupling processes affecting the whole atmosphere, however, continuous radiative transfer calculations are desirable.
In the long-wave regime, frequency-averaged Eddington-type transfer equations are derived for four broad absorber bands. The frequency variation inside each band is parameterized with the Elsasser band model extended by a slowly varying envelope function. This yields additional transfer equations for the perturbation amplitudes which are solved simultaneously together with the mean transfer equations. Deviations from local thermodynamic equilibrium are accommodated in terms of isotropic scattering computed from the two-level model for each band. Solar radiative flux densities are computed for four energetically defined bands using the simple Beer-Bougert-Lambert relation for absorption within the atmosphere. These methods circumvent all the conventionally applied approximations to compute the complicated flux transmission functions that result from formal integration of the radiative transfer equation. The new scheme is implemented in the Kühlungsborn Mechanistic general Circulation Model (KMCM).
First test simulations with low resolution (T32L70) and prescribed concentrations of the radiatively active constituents show quite reasonable results and compare satisfactory to other middle atmospheric GCMs. In particular, since we take the full surface heat budget into account by means of a swamp ocean, and since the internal dynamics and turbulent diffusion of the model are formulated in accordance with the conservation laws, an equilibrated climatological radiation budget is obtained at the top of the atmosphere as well as at the surface. Nevertheless we observe a pronounced annual cycle in the radiation budget at the model top with a positive radiative forcing during late NH winter and a balancing negative forcing during late SH winter. This behavior likely reflects the north-south asymmetry in the dynamic poleward heat transport.
In the future, the new model configuration will be used with high spatial resolutions to explicitly simulate the interaction of gravity waves with the radiation field.
idealized radiationscheme, mechanistic general circulation model, coupling processes
Speaker:
Kouba Daniel
UFA, Praha, Czech Republic
Speaker:
Koucká Knížová Petra
Institute of Atmospheric Physics, Prague 4, Czech Republic
Speaker:
Koval Andrey
Saint-Petersburg State University, Saint-Petersburg, Russia
INTEGRATION OF THE OROGRAPHIC GRAVITY WAVES PARAMETERIZATION IN THE ATMOSPHERIC GENERAL CIRCULATION MODEL.
Authors: Andrey V. Koval, Nikolay M. Gavrilov
Poster presentation
The great contribution into the formation of the general circulation, thermal regime, and composition of the middle and upper atmosphere comes from Internal gravity waves. One of the most important wave sources is the topography of the earth's surface. Oncoming stream wind interacts with the irregularities of the relief, the result is a stationary gravity waves. Using a mathematical model of the generation of atmospheric waves by the mountains and distribution of orographic waves in the middle and upper atmosphere allowed us to develop computer programs for calculating the wave acceleration and heating in the three-dimensional numerical model of general atmospheric circulation. The main new feature of the parameterization developed is using the theory of stationary waves propagation in an inhomogeneous atmosphere for calculating orographic wave accelerations and heating at different altitudes up to the upper atmosphere. Using the atmospheric general circulation model with the inclusion of the parametrization of the orographic waves allowed us to determine the sensitivity of the atmospheric circulation at all altitudes to the effects of the orographic waves.
The parameterization was included in general circulation model MUAM-48 (Middle and upper atmospheric model). The calculated profiles of the wave heating are integrated into the equation of heat and zonal and meridional components of the vector wave acceleration are inserted into the equations of motion.
To calculate the topography the database of earth surface ETOPO2 in increments of 2 minutes along the latitudes and longitudes is used. The exponentially increasing vertical profile of turbulent and molecular viscosity is given. The calculations are performed for the winter and summer seasons.
gravity waves, circulation, atmospheric dynamics
Speaker:
Kyzyurov Yurij
Main Astronomical Observatory NASU, Kiev, Ukraine
SMALL-SCALE IRREGULARITIES IN ELECTRON DENSITY OF THE LOWER IONOSPHERE
Authors: Kyzyurov Yu.
Main Astronomical Observatory NASU, Kiev
Poster presentation
Neutral gas motions play a very important role in dynamics of the ionospheric plasma especially below the turbopause level (100-120 km). In particular, neutral gas turbulence can produce irregularities in the electron density at these altitudes. Because of strong collisional damping at the ionospheric levels not always theory of plasma instabilities can be used to explain generation of fluctuations in electron density. In this report we discuss small-scale irregularities resulted from turbulent mixing of the gas in the lower ionosphere. The irregularity length-scales were restricted to the inertial range of turbulence and were smaller than the local scale of mean plasma-density gradient (which was chosen about 10 km). We considered the irregularity spectra expected from measurements during rocket (or radar) experiments and their dependence on the intensity of turbulence. The consideration was based on an analytic expression for the 3D spectrum of the fluctuations induced by the neutral turbulence in the ionosphere. The derivation of this expression from three-fluid equations is briefly described in the report. It was taken into account that spectrum of random velocity field of gas obeys the power law of Kolmogorov turbulence. The expression gave opportunity to write a formula for evaluation of the rms level of electron-density fluctuations in the given wave-number range. Variability of the 1D spectra expected from experiments was analysed for an irregularity layer in the altitude range 95-105 km (when the magnetic dip angle was 65°45') under intensification of turbulent mixing (the mean rate of turbulent energy dissipation increased from 10 to 100 mW/kg). It was shown that the enhancement of turbulence results in the rise of the rms fluctuation level and in decrease in the slope of irregularity spectrum. The fluctuation level (for the irregularities with length-scale smaller 500 m) near 95 km altitude increased from 2.7 to 2.8 % and near 105 km from 4.4 to 5.0%. If the irregularity spectrum is approximated by a simple power law then the power index increased from –2.12 to –1.95 for h=95 km and from –1.97 to –1.82 for h=105 km. The obtained results are explained by decreasing of the dissipation length-scale from 14.4 to 8.1 m (h=95 km) and from 54.1 to 30.4 m (h=105 km) under the rise of the dissipation rate. The weak change in the fluctuation level results from more important role of turbulent motions with small wave-numbers (large length-scales) in generation of the irregularities.
ionosphere, plasma irregularities, turbulence
Speaker:
Laštovička Jan
Institute of Atmospheric Physics, ASCR, Prague, Czech Republic
IMPACT OF LONG-TERM GLOBAL CHANGE ON VERTICAL COUPLING IN THE ATMOSPHERE-IONOSPHERE SYSTEM
Authors: Jan Laštovička
Institute of Atmospheric Physics ASCR, Bocni II, 14131 Prague, Czech Republic; jla@ufa.cas.cz
The increasing atmospheric concentration of greenhouse gases is known to affect the whole atmosphere-ionosphere system at least to F2-region heights. Also other drivers of long-term changes and trends like long-term change of geomagnetic activity or changes of stratospheric ozone concentration affect significant parts of the atmosphere-ionosphere system. Therefore the vertical coupling in the atmosphere-ionosphere system can also be affected by long-term changes and trends. Here I will present some examples of such effects, as impact of the stratospheric ozone changes on the neutral density in the lower thermosphere and on the E-region ionosphere, or possible long-term changes in the mesopause region winds and atmospheric wave activity. All that clearly indicates that there are three channels of vertical coupling: (1) atmospheric waves, (2) electromagnetic through phenomena like sprites, field-aligned currents etc., and (3) on long-term scale antropogenic changes of concentration of minor chemical constituents (greenhouse gases, ozone etc.).
vertical coupling; long-term change
Speaker:
Liu Libo
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
THE UNUSUAL IONOSPHERE DURING PROLONGED EXTREMELY SOLAR MINIMUM
Authors: Libo Liu*, Yiding Chen, Huijun Le
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
* Also at State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing, 100190, China
Vladimir I. Kurkin, Nelya M. Polekh
Institute of Solar-Terrestrial Physics, Russian Academy of Sciences, Irkutsk, 664033, Russia
and Chien-Chih Lee (cclee@cyu.edu.tw)
General Education Center, Ching-Yun University, Jhungli, Taiwan
A critical question in ionospheric physics is the state of the ionosphere and relevant processes under extremely low solar activity. The solar activity in 2007-2009 is prolonged extremely low, which offers us a unique opportunity to explore this question. In this study, we collected global ionosonde measurements of the F2 layer critical frequency (foF2), E-layer critical frequency (foE) and F-layer virtual height (h’F), and total electron density (TEC) maps produced at Jet Propulsion Laboratory (JPL), which were retrieved from dual-frequency Global Positioning System (GPS) receivers, to investigate the nature of the ionosphere during solar minimum of cycle 23/24, particularly the difference in the ionosphere between solar minima of cycle 23/24 and the preceding cycles. The analysis indicates that the moving 1-year mean foF2 over most available ionosonde stations and global-average TEC went to the lowest during cycle 23/24 minimum. The solar cycle differences in foF2 minima display local time dependence, being larger during the day than at night. Furthermore, cycle difference in daytime foF2 minima is about -0.5 MHz, even reaches to around -1.2 MHz. In contrast, a complex picture presents in global h’F and foE. Evident drop exists in moving 1-year mean h’F at many stations, while no evident differences are found at few stations too. A surprising feature is the increase in foE at some stations, although this feature is not consistent globally; however, the opposite behaviors of foE require independent data for further validation. Further quantitative analysis indicates that record-low foF2 and low TEC can be explained principally in terms of the decrease in solar extreme ultraviolet (EUV) irradiance recorded by SOHO/SEM, which suggests low solar EUV being the prevailing contributor to the unusual low electron density in the ionosphere during cycle 23/24 minimum. It also verifies that a quadratic fitting still reasonably captures the solar variability of foF2 and global-average TEC at such low solar activity levels.
solar cycle; ionosphere; solar minimum
Speaker:
Lu Hua
British Antarctic Survey, Cambridge, United Kingdom
SIGNALS OF SOLAR WIND DYNAMIC PRESSURE IN THE NORTHERN ANNULAR MODE AND THE EQUATORIAL STRATOSPHERIC QUASI-BIENNIAL OSCILLATION
Authors: 1 Hua Lua
1 Martin J. Jarvis
1. British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, United Kingdom
We report statistically measurable responses of the Northern Annular Mode (NAM) and the equatorial stratospheric Quasi-biennial Oscillation (QBO) to solar wind dynamic pressure.
When December to January solar wind dynamic pressure is high, the Northern Hemispheric (NH) circulation response is marked by a stronger polar vortex and weaker sub-tropical jet in the upper to middle stratosphere. As the winter progresses, the Arctic becomes colder and the jet anomalies shift poleward and downward. In spring, the polar stratosphere becomes anomalously warmer.
At solar maxima, significant positive correlations are found between December to January solar wind dynamic pressure and the mid- to late winter NAM all the way from the surface to 20 hPa, implying a strengthened polar vortex, reduced Brewer-Dobson circulation and enhanced stratosphere-troposphere coupling. The combined effect of high solar UV irradiance and high solar wind dynamic pressure in the NH mid- to late winter is enhanced westerlies in the extratropics and weaker westerlies in the subtropics, indicating that more planetary waves are refracted towards the equator. At solar minima, there is no correlation in the NH winter but negative correlations between December to January solar wind dynamic pressure and the NAM are found only in the stratosphere during spring.
Statistical evidence of a possible modulation of the equatorial stratospheric Quasi-biennial Oscillation (QBO) by the solar wind dynamic pressure is also provided. When solar wind dynamic pressure is high, the QBO at 30-70 hPa is found to be preferably more easterly during July to October. These lower stratospheric easterly anomalies are primarily linked to the high frequency component of solar wind dynamic pressure with periods shorter than 3-years. In annually and seasonally aggregated daily averages, the signature of solar wind dynamic pressure in the equatorial zonal wind is characterized by a vertical three-cell anomaly pattern with westerly anomalies both in the troposphere and the upper stratosphere and easterly anomalies in the lower stratosphere. This anomalous behavior in tropical winds is accompanied by a downward propagation of positive temperature anomalies from the upper stratosphere to the lower stratosphere over a period of a year. These results suggest that the solar wind dynamic pressure exerts a seasonal change of the tropical upwelling which results in a systemic modulation of the annual cycle in the lower stratospheric temperature, which in turn affects the QBO during Austral late winter and spring.
These results suggest possible multiple solar inputs. Their combined effect in the stratosphere may cause refraction/redistribution of upward wave propagation and result in projecting the solar wind signals onto the NAM and the QBO. The route by which the effects of solar wind forcing might propagate to the lower atmosphere is yet to be understood.
solar wind dynamic pressure; Northern Annular Mode; Quasi-biennial Oscillation
Speaker:
Maruyama Takashi
Natl. Inst. Information and Communications Technology, Tokyo, Japan
TOTAL ELECTRON CONTENT VARIATIONS AFTER REMOVING SOLAR AND SEASONAL INFLUENCES
Authors: Maruyama T. and Jin H.,
National Institute of Information and Communications Technologies,Tokyo
The major drivers of the ionospheric variations are solar inputs and seasonal changes in the thermosphere. The solar radio flux on 10.7 cm wavelength (F10.7) is widely used as a proxy of solar EUV irradiance that ionizes the neutral atmosphere. However, F10.7 is not a perfect proxy of EUV. Variability of the 10.7 cm flux is mostly due to coronal activities, while EUV originates in various solar atmospheric regions. We used multiple indices to model the solar influences on the ionospheric total electron content (TEC) variations; Mg II c-w-r as a proxy of lower chromospheric activity, SOHO_SEM measurements at 26-34 nm as a proxy of upper chromospheric and transition region activity, and F10.7 as a proxy of transition region to coronal activity. Further, in order to take account of delayed evolutions of activities of active regions related to different proxies, mean values over several preceding periods were used along with the daily values. To deal with multiple solar parameters (9 in total), a seasonal parameter, and ∑Kp representing geomagnetic activities, an artificial neural network (ANN) was used to model the solar, seasonal, and geomagnetic influences. The training of the ANN was conducted for the TEC database covering one solar cycle from 1997 to 2008. The difference (ΔTEC) between the predicted TEC by the trained ANN and the measured TEC is considered to give a time series of TEC variations without solar and seasonal influences, which are most probably driven by the lower atmosphere. A wavelet analysis was applied to the time series of ΔTEC. Strong bursty wave activities with periods of approximately 13 and 27 days were recognized, which are not directly influenced by the solar activity modulations.
TEC, solar proxies, 27-day variations
Speaker:
Mitchell Nicholas
The University Bath , Bath, United Kingdom
Speaker:
Miyoshi Yasunobu
Kyushu University, Fukuoka, Japan
EFFECTS OF THE ATMOSPHERIC WAVES ON VARIATIONS IN THE UPPER ATMSOPEHRE USING AN ATMOSPHERE-IONSOPHERE COUPLED MODEL
Authors: 1 Miyoshi Y., 2 Jin H., 3 Fujiwara H., 2 Shinagawa H., 3 Terada K., 1 Dept. of Earth & Planetary Sciences, Kyushu University, 2 National Institute of Information and Communications Technology, 3 Dept. of Geophysics, Tohoku University
Recent observational and modeling studies have revealed that the energy input from the lower atmosphere produces significant spatial and temporal variations in the thermosphere/ionosphere. For example, the CHAMP observation has shown that the distributions of the neutral temperature and electron density in the equatorial thermosphere/ionosphere have wave-4 pattern in the longitudinal direction. This wave-4 pattern is considered to originate from non-migrating diurnal tide (DE3) that is excited in the troposphere. However, the physical mechanism of spatial and temporal variations in the thermosphere/ionosphere caused by upward propagating atmospheric waves is not fully understood. In order to investigate the physical mechanism of these variations, we developed an atmosphere-ionosphere coupled model, in which a whole atmosphere general circulation model, an ionosphere model and an electrodynamics model are integrated. The coupled model, which is called Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA), is useful for investigating efefcts of upward propagating atmospheric waves on the upper atmospheric behaviors. Using the coupled model, we examine effects of tides, planetary wave and Kelvin wave from the lower atmosphere on the variations in the thermosphere/ionosphere. Our results show that day-to-day variations in the thermosphere/ionsophere are closely related with variations of these upward propagating waves. We also discuss further development of the coupled model in the near future.
day-to-day variations, atmospheric waves, numerical simulation
Speaker:
Mosna Zbysek
IAP, Academy of Sciences, Prague, Czech Republic
UTILISATION OF AUTOMATIC VISUALIZATION OF VIRTUAL HEIGHTS OF IONOSPHERIC LAYERS FOR THE DIGISONDE DPS-4
Authors: 1,2 Mosna, Z., 1, Koucka Knizova, P., 1, Sindelarova, T., 1,2 Kouba, D., 1 Institute of Atmospheric Physics, AS CR, 2, Faculty of Mathematics and Physics, Charles University in Prague
Poster presentation
An automatic method developed for direct access to the virtual heights at chosen range of ionospheric plasma frequencies (digisonde DPS-4, usual cadence is four ionograms per hour) allows us to study the vertical variability of ionospheric layers (e.g., study of gravity or planetary waves), or to give additional information about the type of particular layer for the purpose of Continuous Doppler measurement at stable frequency 3.59 MHz. This method gives us as well rapid overview of ionospheric variability at different plasma frequencies for choosing of time interval of further interest using original digisonde data.
ionospheric sounding, virtual heights, DPS-4, Doppler shift, gravity waves
Speaker:
Nishioka Michi
STEL, Nagoya University, Nagoya, Japan
TEC VARIATIONS ASSOCIATED WITH THE 2010 CHILE EARTHQUAKE STUDIED WITH GROUND-BASED GPS NETWORK DATA
Authors: 1 Nishioka M., 1 Otsuka Y., 1 Shiokawa K., 1 Solar-Terrestrial Environmental Laboratory, Nagoya University, Japan
Poster presentation
Ionospheric variations after the 2010 Chile Earthquake were studied using ground-based GPS receiver data over Chile. The earthquake occurred at 0634UT (0334LT) on February 27, 2010. The magnitude was 8.8. The epicenter located at 35.8S and 72.7W. Around this area, many ground-based GPS receivers are operated by several institutes such as International GNSS Service and Low Latitude Sensor Network. We used more than 60 receivers’ data in order to clarify Total Electron Content (TEC) variations associated the earthquake. Four categories of TEC variations were found associated the earthquake; Category 1. Rapid (~4-5 minutes) enhance, Category 2. Slow (~20 minutes) enhance, Category 3. Depletion, and Category 4. Periodic fluctuation.TEC enhancements such as Categories 1 and 2 have been reported by Otsuka et al. 2006. Properties of the reported enhancement are consistent with those of Categories 1 and 2. Both of rapid and slow TEC enhancements were observed at some stations, which locate ~1000km north of the epicenter. It suggests that two types of TEC enhancements may be generated and propagate individually. Acoustic resonance could also contribute to the periodic fluctuation (Category 4). We will show the characteristics of those TEC variations and discuss the generation mechanism in our presentation.
Total Electron Content, earthquake, acoustic wave, gravity wave
Speaker:
Nozawa Satonori
Nagoya University, Nagoya, Jordan
HIGH LATITUDE LOWER THERMOSHERIC WIND DYNAMICS USING EISCAT AND MF RADARS AND A NEW SODIUM LIDAR
Authors: S. Nozawa1, T. Tsuda1 T. D. Kawahara2, N. Saito3, S. Wada3, S. Oyama1, Y.Ogawa4, C. Hall5, A Brekke5, and R. Fujii1, 1 STEL, Nagoya University, 2 Shinshu University, 3 RIKEN, 4 NIPR, 5 University of Tromsoe
This talk will describe our recent observational results of the wind dynamics in the polar lower thermosphere/mesosphere obtained with EISCAT radars, MF radar, meteor radars, and sodium LIDAR in northern Scandinavia. The polar regions of the Earth's atmosphere hold keys to understanding of a variety of important process such as aurorae, the ozone hole, and global warming. In particular, it is of vital importance to understand more deeply the mesospheric and the lower thermospheric wind dynamics at high latitudes for further understanding of the Magnetosphere-Ionoshpere-Themorpshere coupling process as well as better understanding of atmospheric coupling process between the lower and the upper atmosphere on the earth. It is well known that tidal, gravity and planetary waves play important roles in the wind dynamics in the mesosphere and lower thermosphere (MLT) region, therefore knowledge of the those waves is a key to understand the wind dynamics in MLT region. In this talk, we will present following topic. (1) Mode change of the semidiurnal tide observed between 70 and 120 km in September 2005 at Tromsoe (69.6N, 19.2E). (2) Latitudinal variation of mean winds, tides, and Q2DW in the mesosphere in northern Scandinavia. (3) Temperature variations between 80 and 110 km observed with the new sodium LIDAR at Tromsoe.
Lower thermosphere, tides, mean winds, Q2DW
Speaker:
Nurmukhanbetova Karakoz
Institute of Ionosphere, Almaty, Kazakhstan
A ROLE OF ALTITUDINAL GRADIENT OF THE THERMOSPHERIC WIND SPEED IN F LAYER DYNAMICS OF THE IONOSPHERE
Authors: Nurmukhanbetova K.Zh., Yakovets A.F., Vodyannikov V.V.
In the present study we discuss a role of an altitudinal gradient of the meridional thermospheric wind in the behavior of the vertical structure of the F2 layer of the ionosphere, including variations in peak altitude and bottom of the layer, its half-thickness and electron content on a series of fixed heights during the night electron density enhancement of the winter F2 layer. There were analysed the vertical sounding data for the period of 2000-2009. The nighttime observations of the ionosphere were conducted at the Institute of the Ionosphere (Almaty, 76°55′ E, 43°15′ N), using a digital ionosonde. The continuous observation sessions, each lasting more than 10 night hours, provide ionograms with a time resolution of 5 minutes. We selected eighty three sessions of observations. They are characterized by an enhancement in night electron density in peak altitude and quantitative assessment of the behavior of F2 layer parameters can be obtained with good accuracy. Most of these sessions (73 sessions) were characterized by low geomagnetic activity (Ap <15).Regularly observed effect of a time delay of the moment of the layer bottom motion direction reversal relative to the appropriate moment for the layer maximum allowed to conclude that the reversal of the meridional wind directed towards the pole at day by the wind directed toward the equator at night does not occur simultaneously in the entire thickness of the F2 layer, but with a decreasing of an altitude, the reversal of a direction takes place later. This fact allowed to develop a new method for estimating the downward vertical wind-shear node velocity (V) in the meridional thermospheric wind at altitudes of the ionospheric F2 layer. A distribution of V showed that 86% of it laid in the range of 10-50 m/s with the most probable values at 20-30 m/s. This distribution was compared with a distribution of V obtained from the empirical model of thermospheric winds (HWM93). The comparison has shown that their shapes are very close but most probable values are slightly different. In addition in the study we show that divergent vertical wind-shear node, moving progressively downwards, causes fast increase in thickness of F layer and, as a result, the fast diminution of the electron density because of a plasma redistribution inside the increased thickness of the layer.
Meridional thermospheric wind, ionosphere, F2 layer
Speaker:
Oyama Shin-ichiro
Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan
CHARACTERISTICS OF THE MESOSPHERIC GRAVITY WAVE OBSERVED WITH AN ALL-SKY CAMERA AT TROMSOE, NORWAY IN 2009-2010
Authors: 1 Oyama S., 1 Shiokawa K., 1 Suzuki S., 1 Nozawa S., 1 Otsuka Y., 2 Tsutsumi M., 3 Hall C. M., 4 Meek C., and 4 Manson A., 1 Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya Aichi, Japan, 2 National Institute of Polar Research, Tachikawa Tokyo, Japan, 3 University of Tromsø, Tromsoe, Norway, 4 University of Saskatchewan, Saskatoon, Canada
Poster presentation
An important aspect of the wind dynamics in the mesosphere is to know characteristics of the atmospheric gravity waves, such as propagation direction, zonal and meridional wavenumbers, horizontal wavelength, apparent phase speed, and intensity perturbation amplitude, because it is widely known that the atmospheric gravity waves transport momentum from the lower atmosphere to the mesosphere and the lower thermosphere. Statistical analysis of the OH airglow images measured with all-sky cooled-CCD imagers at low and middle latitudes suggest seasonal, latitudinal dependencies of the wave characteristics. In particular, the wave propagation direction shows clear seasonal variations dependent on latitudes and may also be on longitudes. For example, northward or northeastward propagations are predominant in summer at Rikubetsu (43.5N, 143.8E) and the MU radar site (34.9N, 136.1E), Japan; but westward and southwestward propagation are predominant in winter at Rikubetsu and the MU radar site, respectively. Another statistical result at equatorial region suggests that eastward and westward directions are predominant in winter and summer, respectively, at Kototabang (0.2S, 100.3E), although the propagation direction can be found in all directions. These seasonal, geographical dependencies of the wave propagation direction are controlled by wind filtering, ducting processes, and relative location to the wave source in the lower atmosphere. A new all-sky airglow imager (imager #12 of the Optical Mesosphere Thermosphere Imagers (OMTIs)) was installed at the Ramfjordmoen research station in Norway (69.6N, 19.2E) in January 2009. The imager has a filter wheel to programmatically select one of the six optical filters (557.7 nm, 630.0 nm, OH band (720-1000 nm), 589.3 nm, 572.5 nm, and 732.0 nm) for one exposure interval. This study focuses on the OH airglow images to study the mesospheric gravity waves in winter. The gravity waves predominantly propagate north/northeastward. While we need further investigations of the physical mechanism, the bias of the propagation direction may be attributed to (1) the relative location to the tropospheric low pressure cell, which is typically located around the northern Atlantic Ocean in winter, and/or (2) orographical force by the tropospheric weather system in the Norwegian topography. The observed characteristics of the gravity waves are also compared with the background wind profiles measured with a meteor radar and a MF radar at the same site in order to know the wind filtering effect on the gravity-wave propagation direction.
atmospheric gravity wave, mesosphere, all-sky camera
Speaker:
Pancheva Dora
Geophysical Institute, BAS, Sofia, Bulgaria
GLOBAL IONOSPHERIC RESPONSE TO ATMOSPHERIC TIDES FORCED FROM BELOW
Authors: Dora Pancheva and Plamen Mukhtarov,
Geophysical Institute, Bulg. Acad. Sci., Sofia, Bulgaria
With the recent accumulation of the satellite ionospheric measurements the attention is now being directed towards investigating the impact of wave forcing from the lower atmosphere. Recently, when the level of solar and geomagnetic activity is very low, it is particularly appropriate for investigating the vertical coupling of the atmosphere-ionosphere system by atmospheric waves. The six-satellite Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission makes routine ionospheric measurements over the entire globe using occultation techniques. These observations have been used in to develop global-scale maps of the electron density for altitudes between 100 km and 800 km and for the period of time between January 2008 and March 2009. From the electron density profiles the ionospheric parameters foF2 and hmF2 are obtained as well. These data are used for investigation of the global ionospheric response to the main atmospheric tides forced from below. The temperature measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere-Ionosphere-Mesosphere-Energetics and Dynamics (TIMED) satellite have been analyzed in order to derive the global spatial structure and temporal variability of the above mentioned atmospheric tides (migrating and nonmigrating) from the lower stratosphere to the lower thermosphere (20-120 km). The presentation will be focused mainly to the global distribution and temporal variability of the ionospheric response to the nonmigrating tides responsible for some ionospheric longitudinal structures intensively studied recently.
ionospheric response, migrating and nonmigrating tides, ionospheric longitudinal structure
Speaker:
Petrova Inna
Kazan University, Kazan, Russia
Speaker:
Ren Zhipeng
Institute of Geology and Geophysics Chinese Academy of Sciences, Beijing, China
SIMULATED LONGITUDINAL VARIATIONS IN THE LOWER THERMOSPHERIC NITRIC OXIDE INDUCED BY NON-MIGRATING TIDES
Authors: Zhipeng Ren, Weixing Wan, Libo Liu, and Jiangang Xiong
Based on the GCITEM-IGGCAS model and tides from TIMED/SABER observations, the longitudinal variations in the lower thermosphere nitric oxide (NO), which is induced by non-migrating tides, are investigated. We simulate the intra-annual variation of the NO density, and find that equinoctial lower thermospheric NO density shows an obvious wavenumber-4 longitudinal structure between March and October, and a wavenumber-3 longitudinal structure in other months. These simulation results are consistent with the longitudinal variations observed by Oberheide and Forbes [2008]. The simulations suggest that the wavenumber-4 structure in NO density is driven by the DE3 tide, and the wavenumber-3 structure is driven by the DE2 tide. Our simulations also show that the NO density residuals and the neutral mass density residuals in the height range between 90 and 120km agree well with each other, and the neutral mass density mainly affect the longitudinal variations of lower thermospheric NO density through modulate the chemical production rate.
nonmigrating tides, nitric oxide, thermosphere
Speaker:
Rouslan Latypov
Kazan University, Kazan, Russia
Speaker:
Savenkova Elena
Russian State Hydrometeorological University, Saint-Petersburg, Russia
NONLINEAR INTERACTION AND SATURATION OF PLANETARY WAVES IN THE STRATOSPHERE.
Authors: Elena Savenkova, Anna Kanukhina, Alexander Pogoreltsev
Russian State Hydrometeorological University, St. Petersburg, Russia
The analysis of observations shows that there exists a strong variability of stationary planetary wave (SPW) amplitudes during winter-time in the Northern hemisphere. Using a numerical model of the general circulation, the nonlinear response to an increase of the SPW amplitudes at the lower boundary is investigated. The results obtained show that nonlinear wave-wave and wave-mean flow interactions lead to the saturation of the SPW1 (planetary wave with zonal wave number one). Further increase of the SPW1 forcing at the lower boundary cased a substantial change of the mean flow in the lower stratosphere that limit the vertical penetration of the forced wave into the stratosphere. In result the SPW1 amplitude in the upper stratosphere and mesosphere becomes even smaller in comparison with case of a weak forcing. The analysis of the SPW2 sensitivity in the stratosphere to an increase of the lower boundary forcing shows that in this case the response is approximately linear at least for the realistic (observed) SPW2 amplitudes. A possible application of the results obtained to the problems of the sudden stratospheric warmings, stratospheric vacillations, and spring-time transition is shortly discussed.
dynamics of the middle atmosphere, planetary waves, spring-time transition.
Speaker:
Shagimuratov Irk
WD IZMIRAN, Kaliningrad, Russia
STRUCTURE OF LARGE-SCALE TIDS OBSERVED DURING 11 OCTOBER 2008 STORM
Authors: 1 Shagimuratov I.I., 1 Cherniak Iu.V., 2 Krankovski A., 1 Karpov I.V., 1 WD IZMIRAN, Kaliningrad, Russia, 2 UWM/GRL, Olsztyn, Poland
Poster presentation
During geomagnetic disturbance of 11 October 2008 the unusual day-time positive effect was observed in TEC variations over Europe. Duration of TEC enhancement was of several hours. The short-term surge was also observed at the background of the positive enhancement. This surge was associated with large-scale travelling ionospheric disturbance (TID). Horizontal structure of the TID was analyzed by using of the detailed TEC maps created on the simultaneous GPS observations of EPN. Dynamics of the ionospheric disturbance was ascertained using TEC maps with temporal resolution of 5 min. The striking surge of TEC enhancement was occurred near 12:30UT, its amplitude slowly decreased towards to equator. TID propagated from north to south with speed of about 450 m/s. Vertical structure was investigated on the base of measurements provided by FORMOSAT-3/COSMIC satellite constellation. Enhancement of electron density was observed at all heights, increase in F2 peak region reached the factor of ~2.9.
Ionosphere, geomagnetic storm, GPS, TID
Speaker:
Sharma Shweta
M.L.S. University, Udaipur, Udaipur, India
STUDY OF LOW LATITUDE IONOSPHERE TO THE GEOMAGNETIC STORM OF MAY 2005 OVER DIFFERENT LONGITUDES
Authors: Shweta Sharma, P. Galav and R. Pandey
Department of Physics
Mohanlal Sukhadia University
Udaipur, INDIA
Poster presentation
Response of low latitude ionosphere to the geomagnetic storm of May 2005 has been studied using total electron content (TEC) data obtained from the global positioning system (GPS) receivers. This study was carried out using the receivers that are located near the northern crest (~ 15° N mag. Lat.) of the equatorial ionization anomaly from 55° E to 105° E longitudes. These studies have been substantiated with the ground based magnetometer data at Alibag and Tirunelveli, a low latitude and equatorial station, respectively. The TEC on May 15 reveals two well defined humps as well as TEC modulations. These enhancements have been attributed to the prompt penetration electric fields and delayed equatorial plasma fountain. The traveling atmospheric disturbance (TAD’s) has also been inferred from the low amplitude modulations in the TEC. The solar wind parameters, southward component of inter planetary magnetic field, cross polar cap potential drop, zonal component of the inter planetary electric field and the strength of the equatorial electrojet has also been analyzed for the complete study of disturbed ionospheric conditions.
Low latitude TEC, Geomagnetic storm, TAD
Speaker:
Shepherd Marianna
Centre for Research in Earth and Space Sceince, York University, Toronto, Canada
INVESTIGATION OF MAJOR STRATOSPHERIC WARMING EFFECTS ON ATMOSPHERIC COUPLING AT HIGH LATITUDES USING THE EXTENDED CANADIAN MIDDLE ATMOSPHERE MODEL
Authors: M. G. Shepherd, S. R. Beagley, Y.M. Cho, V. Fomichev, G.G. Shepherd,
Centre for Research in Earth and Space Science, York University, Toronto, Ontario
The study examines the response of the mesosphere/lower thermosphere to the major stratospheric warming (SSW) event from January 2009, as seen in the OH and O2 (0,1) Atmospheric band airglow observations nominally at 87 km and 94 km, respectively by a SATI (Spectral Airglow Temperature Imager) instrument installed at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka (80°N, 86°W) as part of the Canadian Network for the Detection of Atmospheric Change. At the time of the SSW the airglow emissions and the derived rotational temperatures appear depleted and decreased, respectively followed by an enhancement of the airglow emission rates during the SSW recovery phase, while the temperatures returned to their pre-event state. An empirical relationship between OH airglow peak altitude determined by SABER and SATI integrated emission rates allowed perturbed OH and O2 (0,1) airglow altitudes to be assigned to the SATI observations. From these the O volume mixing ratio (VMR), corresponding to the observed OH and O2 (0,1) airglow emission rates were modeled. Atomic oxygen depletion by a factor of ~5 was observed during the SSW and lasted for about 5 days. During the SSW recovery phase the O VMR giving rise to the observed O2 (0,1) airglow emission rates increased by a factor of 3.5 from its pre-SSW level and 17 times from that observed during the peak of the SSW. The observed response of the MLT region to the major stratospheric warming is further examined employing temperature and wind fields, as well as NO and O constituents from the extended Canadian Middle Atmosphere Model (CMAM) at high latitudes from 10 to 220 km height. Temperature and NO observations by the COSMIC/Formosat-3, MLS-Aura and TIMED/SABER satellite experiments are also considered in this study and the results are discussed.
airglow, stratospheric warming, temperature, coupling, modeling
Speaker:
Shetti Dadaso
Smt. Kasturbai Walchand College, sangli, India
SIGNATURE OF MIDNIGHT TEMPERATURE MAXIMUM (MTM) USING TEC (GPS) AND OI630 NM NIGHT AIRGLOW
Authors: 1,3 D.J. Shetti, 3 A.K.Sharma, 2 P.T. Patil, 3 R.V. Bhonsale
1 Smt. Kasturbai Walchand College, Sanglii,416416, India
2Indian Institute of Geomagnetism, New Panvel (E), Navi Mumbai, 410218, India
3 Department of Physics, Shivaji University, Kolhapur, 416004, India.
E-mail – jitushetti@gmail.com
Poster presentation
Night airglow data of Kolhapur station and GPS data of Hyderabad and Bangalore station have been used to obtain OI 630.0 nm intensity emission and d (TEC)/dT values respectively in order to monitor the ionospheric behavior in the Indian region. For this task, we are using the Tilting Photometers and Don Thompson’s slant TEC software (rd_rinex) which gives OI 630.0 nm intensity emission and vertical TEC above each station respectively. The nocturnal variations observed in the atomic oxygen airglow emission at low latitude are well correlated with the dynamical variations seen in the F-region ionospheric parameters such as d(TEC)/dT, for both quiet and disturbed days.The signature of midnight temperature maximum (MTM) has been observed in some of the nights in both OI630.0 nm and d (TEC)/dT data. The signature of MTM has been found in both night airglow (OI630.0 nm) and TEC data. It is suggested that F-region temperature should be simultaneously measured both at equator as well as at Kolhapur to confirm the signature of MTM.
Midnight Temperature Maximum (MTM), GPS , Airglow
Speaker:
Shiokawa Kazuo
Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan
CAWSES-II TASK GROUP 4: WHAT IS THE GEOSPACE RESPONSE TO VARIABLE INPUTS FROM THE LOWER ATMOSPHERE?
Authors: 1 Kazuo Shiokawa, 2 Jens Oberheide, and CAWSES-II Task Group 4, 1 Solar-Terrestrial Environment Laboratory, Nagoya University, 2 Clemson University
Studying the geospace response to variable inputs and waves from the lower atmosphere is particularly important since the induced variability competes with the solar and magnetic driving from above. Consequences for telecommunications, re-entry and satellite operations still need to be explored. The extent to which the effects of this quiescent atmospheric variability are transmitted to the magnetosphere is yet to be resolved. We thus stand right now at an exciting research frontier: understanding the cause-and-effect chain that connects tropospheric and strato-/mesospheric variability with geospace processes. CAWSES-II Task Group 4 (TG4) will therefore elucidate the dynamical coupling from the low and middle atmosphere to the geospace including the upper atmosphere, ionosphere, and magnetosphere, for various frequencies and scales, such as gravity waves, tides, and planetary waves, and for equatorial, middle, and high latitudes. Attacking the problem clearly requires asystems approach involving experimentalists, data analysts and modelers from different communities. For that purpose, the most essential part of TG4 is to encourage interactions between atmospheric scientists and plasma scientists on all occasions. TG4 newsletters are distributed to the related scientists every 3-4 months to introduce various activities of atmospheric and ionospheric researches. Five projects are established in TG4, i.e., Project 1: How do atmospheric waves connect tropospheric weather with ITM variability?, Project 2: What is the relation between atmospheric waves and ionospheric instabilities?, Project 3: How do the different types of waves interact as they propagate through the stratosphere to the ionosphere?, Project 4: How do thermospheric disturbances generated by auroral processes interact with the neutral and ionized atmosphere?, and Project 5: How do thunderstorm activities interact with the atmosphere, ionosphere and magnetosphere? Three campaign observations have been carried out in relation to the TG4 activity, i.e, stratospheric sudden warming campaign (January-February, 2010), longitudinal campaign (September 1-November 12, 2010), and CAWSES Tidal Campaign. In this presentation we show the current status and future plan of CAWSES-II TG4 activities of 2009-2013.
CAWSES-II, Task Group 4, gravity waves, tides, planetary waves, ionosphere, atmosphere
Speaker:
Sidorova Larisa
IZMIRAN, Troitsk Moscow region, Russia
Speaker:
Sindelarova Tereza
Institute of Atmospheric Physics ASCR, Prague 4, Czech Republic
IONOSPHERIC RESPONSE TO METEOROLOGICAL PROCESSES IN DIFFERENT REGIONS. A COMPARISON OF OBSERVATIONS IN CENTRAL EUROPE AND IN SOUTH AFRICA
Authors: 1 Sindelarova T., 1 Chum J., 1,2 Mosna Z., 1 Buresova D., 3,4 McKinnell L.-A., 3,4 Athieno R., 1 Institute of Atmospheric Physics, ASCR, Prague, Czech Republic, 2 Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic, 3 Hermanus Magnetic Observatory, Hermanus, South Africa, 4 Department of Physics & Electronics, Rhodes University, Grahamstown, South Africa
Poster presentation
We study ionospheric effects observed in periods of increased meteorological activity in the troposphere and compare the results obtained in two different regions – in the Czech Republic, Central Europe and in Western Cape, Republic of South Africa. In both regions, similar sounding technique was used. Continuous Doppler frequency shift measurements provide data on wave activity in the ionosphere down to periods of the order of tens of seconds. Information about the stratification of the ionosphere, critical frequencies, and reflection height of the Doppler system sounding wave are obtained from measurements of Digisondes located near both Doppler sounding systems. We selected days with passages of weather fronts over the regions as weather fronts are known as an efficient source of atmospheric waves. The study includes summer and winter events in Northern hemisphere and winter events in Southern hemisphere.
Atmospheric waves, Ionosphere-troposphere coupling, Regional comparison
Speaker:
Sundararaman Sathishkumar
Indian Institute of Geomagnetism, Tirunelveli, India
Speaker:
Takahashi Hisao
INPE, São José dos Campos, Brazil
PLANETARY 2-DAY WAVES IN THE MLT AND IONOSPHERE IN THE SOUTHERN HEMISPHERE LOW LATITUDES
Authors: 1 Takahashi H., 2 Lima L. M., 1 Batista I. S., 1 Onohara A., 1 Batista P. P., 1 Abdu M. A.
1 Instituto Nacional de Pesquisas Espaciais, INPE, São José dos Campos, Brasil, 2 Universidade Estadual de Paraiba, Campina Grande, Brasil
Planetary scale 2-day waves were observed mainly in the January –February time zone in the southern hemisphere low latitude region. Meteor radar wind measurement at Cariri (7.5 S, 35.7 W) from the year 2005 to 2009 showed a distinct 2-day oscillation in the meridional wind with the amplitude of 20 to 50 m/s. The amplitude varied from year to year indicating inter-annual variability of the wave activity. During the same period, the height of ionospheric layer (h´F and constant frequency height) observed at Fortaleza (3.9 S, 38.4 W), near by the Cariri radar station, also showed a similar modulation, indicating influence of planetary 2-day waves in the ionosphere, too. The present work demonstrates simultaneous occurrence of 2-day oscillation in the mesosphere and ionosphere and to study possible effects in the equatorial ionosphere Spread F.
Planetary waves, MLT wind, ionospheric oscillation
Speaker:
Taylor Michael
Center for Atmospheric and Space Sciences, Logan, United States
GRAVITY WAVE ACTIVITY IN THE MLT REGION AND POSSIBLE PROPAGATION INTO THE IONOSPHERE
Authors: 1 Taylor M.J., 1 P.-D. Pautet, 1 T. Martin, Utah State University, Logan, USA
Atmospheric gravity waves (GWs) are known to play key roles in a broad range of dynamical processes extending from Earth’s surface well into the Mesosphere and Lower Thermosphere (MLT) region (~80-100 km) and potentially to higher altitudes. Excited primarily in the lower atmosphere by strong convection, topography, and wind shears, these waves attain large amplitudes as they propagate upwards transporting copious amounts of energy and momentum. Remote sensing optical measurements of the naturally occurring airglow emissions provide an effective method for studying wave occurrence and properties in the MLT region, particularly small-scale, short period (<1 hour) waves which can propagate rapidly (a few hours) from their lower atmospheric sources into the MLT. These events typically exhibit horizontal wavelengths of only a few tens of km yet they can strongly perturb the MLT region due to the onset of wave instability and dissipation effects.
In this study we summarize and compare recent measurements of short-period gravity waves observed at equatorial, mid- and polar latitudes focusing on their seasonal characteristics. We also investigate the potential for larger-scale waves, occasionally evident in these MLT image data, to propagate to higher altitudes well into the lower thermosphere and ionosphere, and compare their properties at different latitudes (where known). These results provide new insight into the “global” occurrence, variability and penetration of gravity waves into the upper reaches of the neutral atmosphere and ionosphere.
Gravity waves, MLT, coupling, ionosphere
SPECTRAL AND SPATIAL SIGNATURES OF UPPER ATMOSPHERIC LIGHTNING PHENOMENA USING IMAGING INSTRUMENTATION
Authors: 1 M.J. Taylor, 1 P.-D. Pautet, 2 M.A. Bailey, 1 Utah State University, Logan, USA, 2 Salisbury University, Salisbury, USA
Sprites, halos, ELVEs and jets are all prominent members of an extraordinary family of Transient Luminous Events (TLEs) that were discovered and named in the 1990’s. Sprites are large vertically structured transient events (few 10s of ms) that can extend from the mesosphere down into the stratosphere (~85-40 km) and are sometimes capped, and briefly preceded (few ms), by a fainter horizontal disk-like halo. Sprites are almost exclusively generated by large positive cloud to ground (CG) lightning discharges whereas halos have been observed by satellite in association with both negative and positive lightning strokes. These types of TLEs are both caused by quasi-static electric fields that excite molecular nitrogen at mesospheric heights to produce N2 first positive band emissions. In contrast, an ELVE is a large (typically 300 km diameter) horizontal donut-shaped flash of light produced by the absorption of an electromagnetic pulse radiated by a powerful lightning discharge as it intersects the base of the nighttime ionosphere (~90-100 km). ELVEs are highly transient (few micro seconds) and are associated with both negative and positive lightning discharges. Jets are even more enigmatic: they originate in the cloud tops and propagate rapidly upwards to the lower ionosphere, branching on the way. Although jets have been imaged on a number of occasions their possible association with lightning events remains unclear. In this talk I will briefly summarize current knowledge on TLEs utilizing video and new high speed image data to exemplify their properties. Recent measurements of TLEs at visible and near infrared wavelengths, in association with both positive and negative lightning will be presented. Possible association of TLEs with powerful terrestrial gamma ray flashes (TGFs) will also be discussed.
Sprites, coupling, thunderstorms, lightning
Speaker:
Tsuda Takuo
STEL, Nagoya Univ., Nagoya, Japan
NEUTRAL TEMPERATURE VARIATIONS OBSERVED WITH A NEW SODIUM LIDAR AT TROMSø, NORWAY
Authors: T. T. Tsuda,1 S. Nozawa,1 T. D. Kawahara,2 N. Saito,3 T. Kawabata,1 S. Wada,3 S. Oyama,1 R. Fujii,1 Y. Ogawa,4 A. Brekke,5 and C. M. Hall5
1STEL, Nagoya Univ., 2Faculty of Engineering, Shinshu Univ.,
3RIKEN, 4National Institute of Polar Research, 5Univ. of Tromsø
Poster presentation
The Earth’s middle and upper atmosphere is a complex and important region, here the neutral particles are interacting with charged particles, and the region is coupled with the lower atmosphere as well as the magnetosphere. In order to advance our knowledge on the coupling between the neutral atmosphere and the ionosphere greatly, it is essential to measure relevant neutral and ionospheric physical parameters simultaneously. To make these kinds of simultaneous measurements, we have installed a new sodium lidar for temperature observations near the European Incoherent Scatter (EISCAT) radar site at Tromsø, Norway (69.6ºN, 19.2ºE). Using the lidar, we have conducted first observations of the lidar at Tromsø during 1-30 October and 13-23 November 2010, and have obtained temperature data of 82 hours. In this presentation, we will report first results of the sodium lidar observations at Tromsø.
Temperature; Mesosphere and lower thermosphere; Polar region; Lidar; EISCAT
NEUTRAL TEMPERATURE VARIATIONS OBSERVED WITH A NEW SODIUM LIDAR AT TROMSO, NORWAY
Authors: 1 T. T. Tsuda, 1 S. Nozawa, 2 T. D. Kawahara, 3 N. Saito, 1 T. Kawabata, 3 S. Wada, 1 S. Oyama, 1 R. Fujii, 4 Y. Ogawa, 5 A. Brekke, 5 C. M. Hall, 1 STEL, Nagoya Univ., 2 Faculty of Engineering, Shinshu Univ., 3 RIKEN, 4 National Institute of Polar Research, 5 Univ. of Tromso
Poster presentation
The Earth’s middle and upper atmosphere is a complex and important region, here the neutral particles are interacting with charged particles, and the region is coupled with the lower atmosphere as well as the magnetosphere. In order to advance our knowledge on the coupling between the neutral atmosphere and the ionosphere greatly, it is essential to measure relevant neutral and ionospheric physical parameters simultaneously. To make these kinds of simultaneous measurements, we have installed a new sodium lidar for temperature observations near the European Incoherent Scatter (EISCAT) radar site at Tromso, Norway (69.6 deg N, 19.2 deg E). Using the lidar, we have conducted first observations during 1-30 October and 13-23 November 2010, and have obtained temperature data of 82 hours. In this presentation, we will report first results of the sodium lidar observations at Tromso.
Temperature; Mesosphere and lower thermosphere; Polar region; Lidar; EISCAT
Speaker:
Turunen Esa
EISCAT Scientific Association, Kiruna, Sweden
VARIATIONS IN THE HIGH-LATITUDE D-REGION IONOSPHERE AS SEEN BY THE EISCAT SVALBARD RADAR DURING THE CONTINUOUS 1-YEAR IPY EXPERIMENT
Authors: Turunen E., Häggström I., EISCAT Scientific Association, Kiruna, Sweden
The EISCAT Svalbard Radar was operated in a continuous type mode during the entire first year of the International Polar Year (IPY) interval, starting on 1 March 2007 and ending on 29 February 2008. The ISR experiment used a specially written IPY mode, which was optimized to ensure also a good coverage in the ionospheric lower E and D regions, in addition to covering the more standard experiment target, the ionospheric F peak and reaching into the topside ionosphere. While the ESR IPY data in the altitude range 100-500 km have been extensively used, for example in studies including the major initiative in high latitude ionospheric modeling, which was supported by funding from the International Space Science Institute in Berne, Switzerland; the low altitude IPY data has not yet been utilized. We present analysis of the ionospheric D-region data, where backscattered power measurements, with 3 km range resolution and 2.25 km steps, start from the altitude of 45 km. Data is subject to sea and/or tropospheric clutter, which is variable with season/day up to 65 km. However, normally data is usable for altitudes higher than 70 km. The ISR experiment does not have enough freqency resolution for advanced doppler and spectral width determinations, but we demonstrate how using a detailed coupled neutral and ion-chemistry model, one can deduce the effect of neutral atmospheric variability in the backscattered power data.
D region, incoherent scatter, neutral atmosphere-ionosphere coupling, International Polar Year
EISCAT_3D: A EUROPEAN IMAGING RADAR FOR ATMOSPHERIC AND GEOSPACE RESEARCH
Authors: 1 Turunen E., and the EISCAT_3D project consortium, 1 EISCAT Scientific Association, Kiruna Sweden
EISCAT_3D will be Europe’s next-generation radar for studies of the high-latitude atmosphere and geospace, with capabilities going beyond anything currently available. The facility will consist of large phased-array receivers and transmitters, distributed in three countries in Northern Scandinavia. EISCAT_3D will comprise tens of thousands, up to more than 100,000 antenna elements. The EISCAT_3D design combines capabilities for volumetric imaging and tracking and aperture synthesis imaging, with improved sensitivity and transmitter flexibility. A minimum of five sites is envisaged, with receivers located around 120 km and 250 km from at least one active site, providing optimal geometry for vectors in the middle and upper atmosphere. An active site comprising 16,000 elements will exceed the sensitivity of the present VHF radar by an order of magnitude. At the passive sites, the design allows the full extent of the transmitted beam to be imaged using holographic techniques. Applications include studies of the atmospheric energy budget, exploration of small-scale and large-scale processes, geospace environment monitoring and service applications. The preparatory phase of the EISCAT_3D project in 2010-2014 is currently funded by EU at the level of 4.5 MEUR. The Preparatory Phase involves the legal, governance, strategic, financial and technical work that is needed before the construction of the radar system can commence.
Incoherent scatter radar, phased array, continuous wind measurements
Speaker:
Usupov Kamil
KFU, Kazan, Russia
FINE STRUCTURE OF SPORADIC E LAYER REFLECTION COEFFICIENT
Authors: A.D. Akchurin, K.M. Usupov
By the ionosonde in Kazan with 1 ionogram per minute long term observation at Es layer echoes was carried out. On a gain curve of Es layer frequency range dependence of amplitude of echoes the deep quasiperiodic variations looked like interference beats are found. Interference located about ~4 MHz in the afternoon and ~2 MHz at night and have extent of ~0.5-2 MHz. A Range between minima increase from 40 to 400 kHz with growth sounding frequency. The approximating dependence as a function distances between local minima with growth of frequency is found. For recover definition beats variations of virtual heights of layers Es with improved precision are investigated. On the base of a difference of heights on various frequency part of a trace, the most probable explanation is the interference magnetoionic component.
ionosonde, structure of Es, interference magnetoionic component of Es echoes
Speaker:
Vlasov Alexey
Russian State Hydrometeorological University, S-Petersburg, Russia
IMPACT OF SOLAR ACTIVITY ON PROPAGATION OF ATMOSPHERIC GRAVITY WAVES THROUGH THE MIDDLE ATMOSPHERE
Authors: 1 Alexey Vlasov, 2 Nikolay Pertsev, 1 Anton Zarubin,1 Alexander Pogoreltsev
1 Russian State Hydrometeorological University, St.-Petersburg, Russia
2 Institute of Atmospheric Physics RAS, Moscow, Russia
Poster presentation
The middle and upper atmosphere can be affected by solar activity in a number of ways, i.e., through a modification of the temperature and wind and/or through the generation and modulation of atmospheric and hydrodynamic waves. The present paper is devoted to study of Atmospheric Gravity Waves (AGW) propagation under different temperature and wind conditions as one of such mechanisms. A set of runs with a linearized numerical model of the plane monochromatic AGW propagation using one of the known empirical spectra and the background conditions (wind and temperature profiles) for different levels of solar activity is performed. The results obtained show that efficiency of the energy and momentum transfer from the lower into the upper atmosphere by the AGW and the mean flow acceleration caused by the AGW dissipation due to thermal conduction and viscosity strongly depends on the level of solar activity. It also has been found that the main effects of the modulation of AGW propagation by the solar activity are observed in the thermosphere. The conclusion that energy and momentum transfer from the lower into the upper atmosphere by AGW and probably other waves is very sensitive to the variability of solar activity.
Atmospheric Gravity Waves, Thermosphere, Middle Atmosphere
Speaker:
Wan Weixing
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
IONOSPHERIC RESPONSES TO THE NON-MIGRATING TIDE DE3: A NUMERICAL SIMULATION
Authors: W. Wan, Z. Ren, F. Ding, J. Xiong, L. Liu, B. Ning, B. Zhao, G. Li and M.-L. Zhang
In this work we numerically investigated the ionospheric responses to the non-migrating atmospheric tide. The diurnal eastward wavenumber-3 (DE3) tidal mode was considered as the low boundary perturbation in the simulation based on the Global Coupled Ionosphere-Thermosphere-Electrodynamics Model, developed by Institute of Geology and Geophysics, Chinese Academy of Sciences (GCITEM-IGGCAS). We then obtained the longitudinal wavenumber-4 (WN4) structure in the ionosphere by running GCITEM-IGGCAS with several devised control conditions. The numerical simulation reveals the coupling processes with which the atmospheric tide DE3 excites the ionospheric WN4 structure. It is found that the direct wave produce the WN4 structure only in neutral parameters (e.g., the mass density). It is noticeable that the phase speed of the mass density WN4 pattern is very large (twice as that of the DE3 tide) at night and small (near to zero) in day time. This is reattributed to the nonlinear interaction between the upward propagated DE3 mode and the local migrating diurnal tide. Our results also show that the DE3 modulated electric field produces the WN4 structure in both the plasma and neutral parameters (e.g., the electron density and mass density). As expected, the latitudinal distribution of this WN4 structure is aligned with the geomagnetic latitude. It is concluded that both the upward propagation of the tidal wave and the electric field coupling play remarkable roles in producing the WN4 structure in thermosphere, and the electric field coupling is the main cause that produce the ionospheric F-region WN4 structure.
longitudinal structure, non-migrating tide, numerical simulation
Speaker:
Ward William
University of New Brunswick, Fredericton, Canada
Speaker:
Wu Qian
National Center for Atmospheric Res, Boulder, United States
MODELING AND OBSERVATION OF MESOSPHERIC TIDE EFFECT ON THE THERMOSPHERE
Authors: 1 Qian Wu, 2 Dave Ortland
1 HAO/National Center for Atmospheric Res., Boulder, CO USA
2 Northwest Research Associates, Bellevue, WA, USA
Poster presentation
Using a TIDI based assimilation model as the lower boundary condition at 95 km, we run the NCAR Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) to simulate the mesospheric tidal effect on the thermosphere. The TIEGCM model is a self-consistent community model. Past observations have shown that the nonmigrating tide can affect the ionosphere. The goal of this study is to understand the contributions from the dynamo effect and tidal propagation. Using the TIDI based assimilation model as the lower boundary condition has two advantages. First it can provide consistent wind, temperature, and geopotential variability at the lower boundary of the TIEGCM. Second, it still contains the seasonal and interannual variations of the TIDI observation. We will show some the of simulation results. Both semidiurnal and diurnal tides will be examined. Comparisons with observation will be provided when data are available.
Tides, mesosphere, thermosphere
Speaker:
Xiong Jiangang
INSTITUTE OF GEOLOGY AND GEOPHYSICS CHINESE ACADEMY OF SCIENCES, Beijing, China
THE QUASI-6.5-DAY DISTURBANCES OF TEC AND THEIR RELATIONSHIP TO THE 6.5-DAY PLANETARY WAVES IN THE MIDDLE ATMOSPHERE
Authors: Jiangang Xiong,Weixin Wan,Libo Liu,
1 Institute of Geology and Geophysics, Chinese Academy of Sciences
The data of igsg-TEC and UKMO data are used to analyze the large scale disturbances in the ionosphere and middle atmosphere from 2002 to 2009. In most years, the 6.5-day disturbance can be found in the ionosphere and middle atmosphere with wavenumber one around spring and autumn equinoxes. The amplitudes of the distubances in ionosphere and middle atmosphere are highly related. The strongest disturbances are all in 2004. The vertical drift of plasma also have similiar variations around two equinoxes. The results show the quasi-6.5-day disturbances in the ionosphere maybe resulted from the quasi-6.5-day waves in the middle atmosphere through interactions between atmosphere and plasma electric fields.
planetary waves, ionosphere, middle atmosphere
Speaker:
Yigit Erdal
University of Michigan, Ann Arbor, United States
COUPLING OF THE LOWER ATMOSPHERE TO THE UPPER ATMOSPHERE VIA SMALL-SCALE GRAVITY WAVES
Authors: 1, Yiğit E.,
2, Medvedev A. S.,
1, University of Michigan, Ann Arbor, USA.
2, Max Planck Institute for Solar System Research, Germany.
Small-scale gravity waves (GWs) cannot be resolved by contemporary general circulation models (GCMs) and it is thus necessary to parameterize their propagation and the resulting effects in order to realistically simulate the atmosphere. It is well established that GWs play an essential role for the momentum budget of the middle atmosphere. However, historically, their propagation into the thermosphere above the turbopause and the resulting effects had not yet been studied either due primarily to the lack of an appropriate GW schemes for the whole atmosphere system or the middle atmosphere GCMs did not extend into the thermosphere. Recently, we have developed an extended nonlinear spectral GW parameterization that physically accounts for the penetration of GWs of lower atmospheric origin into the upper atmosphere, and quantifies the resulting dynamical and thermal effects associated the attenuation of GWs [1]. In addition to nonlinear wave-wave interactions and self-interactions, dissipation of GWs due to additional middle atmospheric and thermospheric physics, such as ion drag, molecular viscosity and conduction, eddy viscosity and radiative damping are accounted for. Simulations with a GCM extending from the lower atmosphere to the upper atmosphere [2-4] suggest that GWs penetrate significantly into the upper
atmosphere up to F2 layer altitudes, and the associated momentum and energy deposition rates are comparable to thermospheric ion drag and Joule heating, respectively. Thus, these results demonstrate the importance of properly parameterizing the effects of small-scale GWs of lower atmospheric origin for better understanding the morphology of the upper atmosphere. Also, properly accounting for GW dissipation above the turbopause is shown to improve GCM simulations with respect to two widely used empirical models of the upper atmosphere.
References:
[1] Yiğit, E., A. D. Aylward, A.S. Medvedev (2008), J. Geophys. Res., 113, D19106,
doi:10.1029/2008JD010135.
[2] Yiğit, E., and A. S. Medvedev (2010), J. Geophys. Res., 115, A00G02, doi:10.1029/2009JA015106.
[3] Yiğit, E., and A. S. Medvedev (2009), Geophys. Res. Lett., 36, L14807, doi:10.1029/2009GL038507.
[4] Yiğit, E., A. S. Medvedev, A. D. Aylward, P. Hartogh, and M. J. Harris (2009),
J. Geophys. Res., 114, D07101, doi:10.1029/2008JD011132.
Gravity propagation and dissipation. Thermosphere. General Circulation Models. Wave heating/cooling
Speaker:
Zakharenkova Irina
WD IZMIRAN, Kaliningrad, Russia
IONOSPHERIC ELECTRON CONTENT OVER EUROPEAN MID-LATITUDES AND ITS COMPARISON WITH GPS TEC MEASUREMENTS
Authors: 1 Zakharenkova I.E., 1 Shagimuratov I.I., 2 Krankowski A., 2 Krypiak-Gregorczyk A., 1 WD IZMIRAN, Kaliningrad, Russia, 2 UWM/GRL, Olsztyn, Poland
FormoSat-3/COSMIC (F3/C) now provides unprecedented global coverage of GPS occultations measurements, each of which yields the ionosphere electron density information with high vertical resolution. This report is focused on the study of the electron density profiles derived from F3/C radio occultation (RO) measurements. The region of the European mid-latitudes with 2 closely located ionosonde stations – Pruhonice (50.0 E, 14.6 N) and Juliusruh (54.6 E, 13.4 N) – was considered. The F3/C RO profiles were selected if the tangential points of the signal ray path were within the limits of the considered region. Also the total electron content (TEC) values were calculated using the observations of the nearest ground-based GPS stations located in European region. To compare GPS TEC with F3/C RO and ionosondes’ data these profiles were integrated. So, comparison of GPS TEC, F3/C IEC and ionosonde IEC was carried out for different seasonal conditions during period of low solar activity. Special attention was focused on the differences in topside and bottomside parts of the ionosphere, as F3/C provided experimental data while topside ionosonde profile is obtained by fitting a model to the peak electron density value. GPS TEC values are greater than F3/C and ionosonde data as GPS TEC contains IEC and PEC (plasmaspheric electron content). This procedure can be useful to estimate the impact of PEC into TEC. Results of the comparative analysis between GPS TEC and IEC with changes in bottomside, topside and PEC are presented for quiet and disturbed geomagnetic conditions.
Ionosphere, GPS TEC, IEC, radio occultation
