Browse Articles
Characterization and Climatological Modeling of Equatorial Ionization Anomaly (EIA) Crest Position
-  25 November 2022
Key Points
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At higher altitudes the crests of Equatorial Ionization Anomaly (EIA) are found closer to the dip equator than the crests at lower altitude
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The positions of the EIA crests show a weak linear correlation with solar radio flux (F10.7)
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Empirical models for the position of EIA crests are developed
Survey of Electron Heating and Implications for Wave-Particle Interactions Near the Lunar Surface: ARTEMIS Observations
-  24 November 2022
Key Points
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Electron heating near the lunar surface is observed in association with electrostatic and electromagnetic waves
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Perpendicular electron heating is associated with electron cyclotron drift instability and correlated with the reflected ion density ratio
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Parallel electron heating is associated with electron two-stream instabilities and suggestive of modified two-stream instabilities
Modeling Solar Eclipses at Extreme Ultra Violet Wavelengths and the Effects of Nonuniform Eclipse Shadow on the Ionosphere-Thermosphere System
-  24 November 2022
Key Points
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A model of solar eclipses at extreme ultraviolet (EUV) wavelengths is introduced that takes Solar Dynamics Observatory Atmospheric Imaging Assembly and GOES-R Solar Ultraviolet Imager images as the input
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GITM simulations reveal the impacts of the EUV eclipse mask contribute about 20% to the ionosphere-thermosphere response
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The EUV eclipse model is validated using PRoject for Onboard Autonomy 2/Large Yield Radiometer in situ measurements of solar irradiance flux during eclipse passes
Correlation Between Bandwidth and Frequency of Plasmaspheric Hiss Uncovered With Unsupervised Machine Learning
-  23 November 2022
Key Points
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Unsupervised machine learning is used to categorize hiss power spectra of the electric field from Van Allen Probes
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From the pre-noon sector toward the afternoon sector the hiss frequency decreases while the bandwidth increases
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We discuss possible source mechanisms that are consistent with the spatial distribution of the hiss waves
Coordinated Observations of Migrating Tides by Multiple Meteor Radars in the Equatorial Mesosphere and Lower Thermosphere
-  23 November 2022
Key Points
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The diurnal and semidiurnal migrating tides are derived by multi-meteor radars in the equatorial region
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The seasonal variations of diurnal westward-propagating zonal wavenumber 1 (DW1) and semidiurnal westward-propagating zonal wavenumber 2 (SW2) observations are similar to those tidal components in Climatological Tidal Model of the Thermosphere modeling
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The unusual enhancements of DW1 and SW2 in February 2006 are possibly associated with the 2006 Northern Hemisphere stratospheric sudden warming event
Auroral Field-Aligned Current Signatures in Jupiter's Magnetosphere: Juno Magnetic Field Observations and Physical Modeling
-  22 November 2022
Key Points
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Upward field-aligned currents ∼400 nA m−2 are seen at high altitudes (r ∼ 4–16 RJ) on northern auroral field lines on 10 inbound Juno passes
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Sheets in opposite longitude sectors carry factor ∼2 different mean currents, the larger ∼4 to 10 MA rad−1 being comparable with model values
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Low-altitude (r < ∼2 RJ) auroral currents reported on the same passes are correlated (R ∼ 0.7) but overall lower in magnitude ∼4 MA rad−1
Writhed Analytical Magnetic Flux Rope Model
-  21 November 2022
Key Points
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We develop an analytical model that can be used to describe writhed flux ropes by describing the flux rope axis as a general space curve
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We show how this model can be implemented numerically in terms of quadratic splines and configured for an arbitrary twist distribution
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We find that the field lines resulting from our model have lower twist per unit length than would be expected from a toroidal approximation
Energetic Magnetospheric Particle Fluxes Onto Callisto's Atmosphere
-  18 November 2022
Key Points
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We calculate the effect of Callisto's perturbed electromagnetic environment on energetic particle fluxes onto the top of the atmosphere
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Electron flux patterns are strongly affected by Callisto's plasma interaction, while ion fluxes are nearly uniform in the perturbed fields
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Fluxes onto the exobase are largest within the Jovian current sheet, despite strong field perturbations generated by the plasma interaction
Statistical Study of the Relationship Between Pi1/2-Band Wave Powers and Firehose Instability Criterion During Fast Flows in the Magnetotail Plasma Sheet
-  17 November 2022
Key Points
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The probability of the firehose unstable condition near the neutral sheet (NS) during fast flows tends to be larger for the faster flow
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The Pi1/2-band wave powers during fast flows are associated with the threshold of firehose instabilities as well as the fast flow velocity
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The firehose unstable condition might affect the Pi1/2-band wave powers during fast flows with a certain average velocity near the NS
In situ space plasma diagnostics with finite amplitude active electric experiments: Non-linear plasma effects and instrumental performance of mutual impedance experiments
-  2 December 2022
Key Points
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The plasma response to large antenna emission amplitudes triggering non-linear plasma perturbations is simulated
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Ion dynamics contributions to large amplitude propagating electric signals in the plasma are crucial and therefore should not be neglected
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Mutual impedance diagnostic performances are acceptable for emission amplitudes corresponding to electric-to-kinetic energy ratios up to 0.1
On a Guiding of Whistler-Mode Waves by Density Gradients
-  2 December 2022
Key Points
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Localized packages of VLF whistler-mode waves are frequently observed by satellites in the vicinity of density gradients
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We model the guiding of these waves by the density gradients using equations of electron magnetohydrodynamics
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We show that the whistler-mode wave can be guided by plasma gradients with a size less than the characteristic transverse size of the wave
Multi-step vertical coupling during the January 2017 sudden stratospheric warming
-  29 November 2022
Key Points
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Wintertime thermospheric GWs simulated by the HIAMCM are strongly reduced during the January 2017 SSW and the subsequent weak-vortex period
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Observed quiettime TEC perturbations show reduced amplitudes during the SSW and weak-vortex period as well
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Propagation directions, wavelengths, and periods of the simulated thermospheric GWs agree with observed quiettime TEC perturbations
Stormtime ring current heating of the ionosphere and plasmasphere
-  28 November 2022
Key Points
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CIMI-computed ring current heating is coupled into SAMI3 to drive a simulation of the stormtime ionosphere and plasmasphere
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The CIMI-simulated model ring current is shown to directly heat both the plasmasphere and ionosphere
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When the model ring current heating is limited to plasmasphere heights, elevated ionosphere temperatures are similar to observations
A MAVEN case study of radial IMF at Mars: Impacts on the dayside ionosphere
-  28 November 2022
Key Points
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During radial interplanetary magnetic field conditions at Mars, the magnetic barrier forms deep within the dayside ionosphere
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Planetary ions above the magnetic barrier are exposed to the solar wind flow and coupled via weak VxB and strong wave particle interactions
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Plasma temperatures are enhanced by factors of 2-10 within the ionosphere; concurrently the dayside ionosphere is significantly eroded
Diagnostic analysis of the physical processes underlying the long-duration ΣO/N2 depletion during the recovery phase of the 8 June 2019 geomagnetic storm
-  27 November 2022
Key Points
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A long-duration ∑O/N2 depletion was observed by GOLD over the Atlantic Ocean during the recovery phase of a geomagnetic storm
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Vertical advection and molecular diffusion dominated the initial recovery of the ∑O/N2 depletion
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In the late recovery phase, the recovery of the perturbations was mainly determined by horizontal advection
Magnetic storms during the space age: Occurrence and relation to varying solar activity
-  25 November 2022
Key Points
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We explain the occurrence of magnetic storms in space age by their relation to the varying solar activity and solar magnetic structure
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he occurrence of large, moderate and weak HSS/CIR storms follows the decrease of the HCS tilt in the declining phase of solar cycle
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Maxima of HSS/CIR storms have shifted from late declining phase in cycles 20-22 to earlier times in cycles 23-24 due to recent HCS widening
Properties of turbulent Alfvénic fluctuations and wave-particle interaction associated with Io’s footprint tail
-  23 November 2022
Key Points
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Low-frequency Juno observations in the Io flux tube tail represent structures perpendicular to background magnetic field
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Magnetic field fluctuations observed in the IFPT are consistent with weak-MHD and sub-ion kinetic Alfvén wave turbulence
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Dispersion effects on group velocity of Alfvén waves widens the Io flux tube consistent with the observed width of the IFPT
Comparing Jupiter’s equatorial X-ray emissions with solar X-ray flux over 19 years of the Chandra mission
-  16 November 2022
Key Points
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We present a statistical study of jovian disk X-rays from 19 years worth of Chandra data showing a strong correlation with solar X-ray flux
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Jovian disk emissions are predominantly governed by solar activity. Pearson’s Correlation Coefficient of 0.9 found between the data
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Analysis of spatial morphology of the disk emissions reveals preference of disk emission at 2-3.5 Gauss magnetic field strength
Topology of Magnetic and Velocity Fields at Kinetic Scales in Incompressible Plasma Turbulence
-  31 October 2022
Key Points
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The kinetic-scales topological features in incompressible magnetosheath plasma turbulence are investigated
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Distribution patterns different from hydrodynamic and magnetohydrodynamic turbulence of velocity-field topological characteristics are identified
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Sheet-like structures dominate dissipation-scale dynamics in the incompressible plasma turbulence
NRLMSISE-00 empirical model of the atmosphere: Statistical comparisons and scientific issues
- Journal of Geophysical Research: Space Physics
-  SIA 15-1-SIA 15-16
-  24 December 2002
What is a geomagnetic storm?
- Journal of Geophysical Research: Space Physics
-  5771-5792
-  1 April 1994
Solar wind spatial scales in and comparisons of hourly Wind and ACE plasma and magnetic field data
- Journal of Geophysical Research: Space Physics
-  16 February 2005
Modeling the dynamics of the inner magnetosphere during strong geomagnetic storms
- Journal of Geophysical Research: Space Physics
-  15 March 2005
The SuperMAG data processing technique
- Journal of Geophysical Research: Space Physics
-  14 September 2012
Key Points
- A weak residual ring current is always present
- Automated baseline determination technique
- Determination of local magnetic coordinate system
Collision frequency of artificial satellites: The creation of a debris belt
- Journal of Geophysical Research: Space Physics
-  2637-2646
-  1 June 1978
Magnetic loop behind an interplanetary shock: Voyager, Helios, and IMP 8 observations
- Journal of Geophysical Research: Space Physics
-  6673-6684
-  1 August 1981
The ionospheric disturbance dynamo
- Journal of Geophysical Research: Space Physics
-  1669-1686
-  1 April 1980
Magnetopause location under extreme solar wind conditions
- Journal of Geophysical Research: Space Physics
-  17691-17700
-  1 August 1998
Geospace Environmental Modeling (GEM) Magnetic Reconnection Challenge
- Journal of Geophysical Research: Space Physics
-  3715-3719
-  1 March 2001
Quasi two day wave-related variability in the background dynamics and composition of the mesosphere/thermosphere and the ionosphere
- Journal of Geophysical Research: Space Physics
-  4786-4804
-  15 May 2014
Key Points
- Dissipating planetary waves (PWs) in the MLT can drive background wind changes
- Mixing from dissipating PWs drive thermosphere/ionosphere composition changes
- First observations of QTDW-driven variability from this mechanism
Effect of the altitudinal variation of the gravitational acceleration on the thermosphere simulation
- Journal of Geophysical Research: Space Physics
-  4 September 2008
Earth's Van Allen Radiation Belts: From Discovery to the Van Allen Probes Era
- Journal of Geophysical Research: Space Physics
-  8319-8351
-  23 November 2019
Key Points
- A brief historical background on the discovery of the Van Allen radiation belts and their response to solar activity is introduced
- Recent advances in understanding mechanisms responsible for radiation belt electron acceleration, transport, and loss are reviewed
- Outstanding challenges for developing future radiation belt models are summarized
Plain Language Summary
Discovery of the Earth's Van Allen radiation belts by instruments flown on Explorer 1 in 1958 was the first major discovery of the Space Age. The dynamic properties of trapped outer zone electrons and the outer boundary of the inner zone proton population, along with source populations, have recently been studied in great detail by instruments on National Aeronautics and Space Administration's Van Allen Probes spacecraft, as well as other data sources like operational spacecraft designed for navigation and terrestrial weather forecasting. The vulnerability of the myriad of spacecraft that is strongly affected by space weather disruptions, as compared to 1958, has motivated the radiation belt community to develop essential improved models for forecasting the space environment we will inhabit in the 21st century and evaluate its impacts on our technological society. In this paper, we provide a review on historical background and recent advances in understanding and modeling acceleration, transport, and loss processes of energetic particles in the Earth's Van Allen radiation belts, followed by outstanding challenges for developing future radiation belt models. The findings on the fundamental physics of the Van Allen radiation belts potentially provide insights into understanding energetic particle dynamics at other magnetized planets in the solar system, exoplanets throughout the universe, as well as in astrophysical and laboratory plasmas. Given the potential Space Weather impact of radiation belt variability on technological systems, these new radiation belt models are expected to play a critical role in our technological society in the future much as meteorological models do today.
Magnetic Reconnection in the Space Sciences: Past, Present, and Future
- Journal of Geophysical Research: Space Physics
-  15 December 2019
Key Points
- Magnetic reconnection is a key energy conversion and transport process in plasmas
- There has been recent, considerable, research progress understanding how reconnection works
- Many exciting research challenges await, while we can reap the benefits of our new understanding
Plain Language Summary
In space, huge amounts of energy are released explosively by a mysterious mechanism: magnetic reconnection. Reconnection can abruptly convert energy stored in magnetic fields to energy in charged particles, and power such diverse phenomena as solar and stellar flares, magnetic storms and aurorae in near-Earth space, and major disruptions in magnetically confined fusion devices. It is behind many of the dangerous effects associated with space weather, including damage to satellites, endangering astronauts, and impacting the power grid and pipelines. Understanding reconnection enables us to quantitatively describe and predict these magnetic explosions. Therefore, magnetic reconnection has been at the forefront of scientific interest for many years, and will be for many more. Measuring reconnection is incredibly difficult. However, recently scientists have been able to peek into its machinery. Combining measurements from NASA's Magnetospheric Multiscale mission with supercomputer modeling, scientists have now been able to analyze the inner workings of this elusive mechanism. Even though open questions remain, this new understanding has broad implications. Here, we describe magnetic reconnection, where it plays a role, its impacts on society, and what we now know about it. We point to future research challenges, including implications and the utility of our recently developed knowledge.
SWAN/SOHO Lyman-α Mapping: The Hydrogen Geocorona Extends Well Beyond the Moon
- Journal of Geophysical Research: Space Physics
-  861-885
-  15 February 2019
Key Points
- We find that the geocorona extends to almost twice the distance of the Moon
- the H exosphere is compressed by solar radiation pressure, forming a bulge on the dayside
- this bulge is enhanced at low solar activity, possibly in relation with a population of Hatoms in satellite orbits
NRLMSISE-00 empirical model of the atmosphere: Statistical comparisons and scientific issues
- Journal of Geophysical Research: Space Physics
-  SIA 15-1-SIA 15-16
-  24 December 2002
Occurrence Distribution of Polar Cap Patches: Dependences on UT, Season and Hemisphere
- Journal of Geophysical Research: Space Physics
-  14 December 2020
Key Points
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Statistics show that the occurrence rate of patches is a complex function of UT, season and hemisphere
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But, the occurrence distribution can be interpreted by the spatial overlap between the high-latitude convection and the solar terminator
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Outstanding interhemispheric difference is found in the UT and seasonal distribution of patches
Plain Language Summary
In the upper part of the ionosphere at the highest latitudes of the Earth, we often observe isolated chunk of high-density plasma at around 300 km altitude. Those localized regions of enhanced plasma density is called “polar cap patches”. Polar cap patches are known to occur when the interplanetary magnetic field (IMF) is directed southward and the magnetosphere-ionosphere coupling system becomes open to the energy input from the solar wind. Of course, the direction of IMF is an important factor which determines the production of patches. But, we still do not know what controls the diurnal and seasonal variations of patch activity. To answer this question, we have carried out a statistical analysis of the occurrence probability of polar cap patches by using the in situ plasma density data from the low-Earth orbiting satellite Swarm. The statistics clearly show that the diurnal and seasonal variations of patch activity are strongly characterized by the spatial overlap between the high-latitude convection and the high density source plasma in the sunlit region. The statistics also demonstrate the existence of remarkable interhemispheric difference in the patch occurrence distribution, which can be interpreted by the difference in the offset between the geographic and geomagnetic poles between the two hemispheres.
Persistence of the Gleissberg 88-year solar cycle over the last ∼12,000 years: Evidence from cosmogenic isotopes
- Journal of Geophysical Research: Space Physics
-  SSH 1-1-SSH 1-15
-  3 January 2003
Application of Cold and Hot Plasma Composition Measurements to Investigate Impacts on Dusk-Side Electromagnetic Ion Cyclotron Waves
- Journal of Geophysical Research: Space Physics
-  9 December 2020
Key Points
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Plasma bulk flows enabled direct measurement of cold plasmaspheric ions during dusk-side EMIC wave activity
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The cold and hot plasma composition data supported accurate tests of local linear wave growth
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The presence and variability of heavy ions impact wave growth and band structure, and can influence subsequent wave-particle interactions
Plain Language Summary
Electromagnetic ion cyclotron (EMIC) waves occur throughout our solar system. The waves have been observed near Earth and are more likely to achieve large amplitudes in the magnetized plasma that exists in a region of space called Earth's dusk-side magnetosphere. Multiple plasma populations exist in this region that can be organized into groups of cold or hot plasmas. Although the hot plasmas can be measured most of the time, the cold plasmas are usually hidden from plasma sensors due to positive spacecraft charging issues; cold plasmas are therefore usually unavailable to help provide a detailed understanding of why dusk-side EMIC waves are generated. The purpose of our study was to investigate measurements made by the NASA Magnetospheric Multiscale satellites to during a time period when the cold plasma species were not hidden and apply these measurements to improve understanding of these dusk-side EMIC waves. The results showed why comprehensive measurements are needed to continue advancing our understanding of EMIC waves as seen by other spacecraft in different regions in Earth's magnetosphere, and how these waves impact other plasma populations.
Ring Current Decay During Geomagnetic Storm Recovery Phase: Comparison Between RBSP Observations and Theoretical Modeling
- Journal of Geophysical Research: Space Physics
-  7 December 2020
Key Points
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The observed lifetime of ring current ions (H+ and O+) are obtained and compared with theoretical predictions of charge exchange lifetime
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The observed lifetimes of H+ is short than that of O+ when E < ∼50 keV while the situation is reversed when E > ∼50 keV
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The charge exchange lifetime estimations of ions are in good agreement with observed lifetimes