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
Speaker:
Candido Claudia
INPE, Sao Jose dos Campos, Brazil
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
Speaker:
England Scott
University of California Berkeley, Berkeley, United States
Speaker:
Fukushima Daisuke
Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan
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 AND PLANETARY WAVE COUPLING OF LOW LATITUDE ATMOSPHERE-IONOSPHERE SYSTEM: LONGITUDINAL VARIABILITIES
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
Speaker:
http://avtozastivxux.sweb.cz http://avtozastivxux.sweb.cz
http://avtozastivxux.sweb.cz, New York, Afghanistan
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:
kherani esfhan alam
instituto nacional de pesquisais espaciais, sao jose dos campos, Brazil
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
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:
Maruyama Takashi
Natl. Inst. Information and Communications Technology, Tokyo, Japan
Speaker:
Mosna Zbysek
IAP, Academy of Sciences, Prague, Czech Republic
Speaker:
Nishioka Michi
STEL, Nagoya University, Nagoya, Japan
Speaker:
Nozawa Satonori
Nagoya University, Nagoya, Jordan
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
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:
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:
Shetti Dadaso
Smt. Kasturbai Walchand College, sangli, India
Speaker:
Shiokawa Kazuo
Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan
Speaker:
Sundararaman Sathishkumar
Indian Institute of Geomagnetism, Tirunelveli, India
Speaker:
Taylor Michael
Center for Atmospheric and Space Sciences, Logan, United States
Speaker:
Tsuda Takuo
STEL, Nagoya Univ., Nagoya, Japan
Speaker:
Usupov Kamil
KFU, Kazan, Russia
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:
Yiğit Erdal
University of Michigan, Ann Arbor, United States
