Alexander Drozdov

Planetary Science Institute

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Yuri Shprits

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Dedong Wang

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Nikita Aseev

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Adam Kellerman

University of California, Los Angeles

A. Saikin

Planetary Science Institute

Hayley Allison

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

G. D. Reeves

Los Alamos National Laboratory

Irina Zhelavskaya

Huawei Technologies (China)

Artem Smirnov

Ludwig-Maximilians-Universität München

R. B. Horne

British Antarctic Survey

Cooperative Institutions

University of Colorado Boulder

University of California, Los Angeles

University of California, Berkeley

Goddard Space Flight Center

Planetary Science Institute

Charles River Laboratories (Netherlands)

Nagoya University

Laboratory for Atmospheric and Space Physics

John Wiley & Sons (United States)

Johns Hopkins University Applied Physics Laboratory

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Chorus Waves and Their Effect on Energetic Electrons in the Inner-magnetosphere

Dedong Wang Yuri Shprits Bernhard Haas Alexander Drozdov Angelica Castillo

Chorus

10.46620/ursiatrasc24/upfr1922

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Citations (0)

Energetic, relativistic, and ultrarelativistic electrons: Comparison of long‐term VERB code simulations with Van Allen Probes measurements

Journal of Geophysical Research Space Physics (2015)

Alexander Drozdov Yuri Shprits K. Orlova Adam Kellerman D. Subbotin

Abstract In this study, we compare long‐term simulations performed by the Versatile Electron Radiation Belt (VERB) code with observations from the Magnetic Electron Ion Spectrometer and Relativistic Electron‐Proton Telescope instruments on the Van Allen Probes satellites. The model takes into account radial, energy, pitch angle and mixed diffusion, losses into the atmosphere, and magnetopause shadowing. We consider the energetic (>100 keV), relativistic (~0.5–1 MeV), and ultrarelativistic (>2 MeV) electrons. One year of relativistic electron measurements ( μ = 700 MeV/G) from 1 October 2012 to 1 October 2013 are well reproduced by the simulation during varying levels of geomagnetic activity. However, for ultrarelativistic energies ( μ = 3500 MeV/G), the VERB code simulation overestimates electron fluxes and phase space density. These results indicate that an additional loss mechanism is operational and efficient for these high energies. The most likely mechanism for explaining the observed loss at ultrarelativistic energies is scattering by the electromagnetic ion cyclotron waves.

Van Allen Probes

Pitch angle

10.1002/2014ja020637

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The Effect of Plasma Boundaries on the Dynamic Evolution of Relativistic Radiation Belt Electrons

Journal of Geophysical Research Space Physics (2020)

Dedong Wang Yuri Shprits Irina Zhelavskaya Frederic Effenberger Angelica Castillo

Abstract Understanding the dynamic evolution of relativistic electrons in the Earth's radiation belts during both storm and nonstorm times is a challenging task. The U.S. National Science Foundation's Geospace Environment Modeling (GEM) focus group “Quantitative Assessment of Radiation Belt Modeling” has selected two storm time and two nonstorm time events that occurred during the second year of the Van Allen Probes mission for in‐depth study. Here, we perform simulations for these GEM challenge events using the 3D Versatile Electron Radiation Belt code. We set up the outer L * boundary using data from the Geostationary Operational Environmental Satellites and validate the simulation results against satellite observations from both the Geostationary Operational Environmental Satellites and Van Allen Probe missions for 0.9‐MeV electrons. Our results show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. The magnetopause shadowing effect is included by using last closed drift shell, and it is shown to significantly contribute to the dropouts of relativistic electrons at high L * . We perform simulations using four different empirical radial diffusion coefficient models for the GEM challenge events, and the results show that these simulations reproduce the general dynamic evolution of relativistic radiation belt electrons. However, in the events shown here, simulations using the radial diffusion coefficients from Brautigam and Albert (2000) produce the best agreement with satellite observations.

Van Allen Probes

Plasmasphere

10.1029/2019ja027422

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Citations (33)

Jupiter's Whistler‐Mode Belts and Electron Slot Region

Journal of Geophysical Research Space Physics (2024)

Yixin Hao Yuri Shprits J. D. Menietti Zhi‐Yang Liu T. F. Averkamp

Abstract The spatial distribution of whistler‐mode wave emissions in the Jovian magnetosphere measured during the first 45 perijove orbits of Juno is investigated. A double‐belt structure in whistler‐mode wave intensity is revealed. Between the two whistler‐mode belts, there exists a region devoid of 100 s keV electrons near the magnetic equator at . Insufficient source electron population in such an electron “slot” region is a possible explanation for the relatively lower wave activity compared to the whistler‐mode belts. The wave intensity of the outer whistler‐mode belt measured in the dusk‐premidnight sector is significantly stronger than in the postmidnight‐dawn sector. We suggest that the inherent dawn‐dusk asymmetries in source electron distribution and/or auroral hiss emission rather than the modulation of solar cycle are more likely to result in the azimuthal variation of outer whistler‐mode belt intensity during the first 45 Juno perijove orbits.

Whistler

Jupiter (rocket family)

Pitch angle

Intensity

10.1029/2024ja032850

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Ring current electron precipitation during the 17 March 2013 geomagnetic storm: Underlying mechanisms and their effect on the atmosphere

Advances in Space Research (2024)

Alina Grishina Yuri Shprits Alexander Drozdov Miriam Sinnhuber Florian Haenel

Electron and ion fluxes at energies of ∼ 10 keV - 1 MeV can change by orders of magnitude during geomagnetically active periods. This can lead to intensification of particle precipitation into the Earth's atmosphere. The process further affects atmospheric chemistry, which may impact weather and climate on the Earth's surface. In this study, we concentrate on ring current electrons, and investigate precipitation mechanisms using a numerical model based on the Fokker-Planck equation. We focus on a study of the main precipitation mechanisms, and their connection with atmospheric parameters. We investigate the 17 March 2013 storm using the convection-diffusion 4-Dimensional Versatile Electron Radiation Belt (VERB-4D) code, that allows us to quantify the impact of the storm on the electron ring current, and the resulting electron precipitation. We validate our results against observations from the Polar Operational Environmental Satellites (POES) mission, the low Earth orbiting meteorological satellites National Oceanic and Atmospheric Administration (NOAA-15,-16,-17,-18,-19), and Meteorological Operational Satellite MetOp-02, as well as the Van Allen Probes, and produce a data set of precipitating fluxes that covers an energy range from 10 keV to 1 MeV. We calculate the altitude-dependent atmospheric ionization rates, a prerequisite for atmospheric models to estimate effects of geomagnetically active periods on chemical and physical variability of the atmosphere at high latitudes. Atmospheric ionization rates are validated against Atmospheric Ionization during Substorm (AIMOS 2.1-Aisstorm) and Special Sensor Ultraviolet Spectrographic Imagers (SSUSI) values, and show good agreement at high geomagnetic latitudes during the storm time.

Ring current

Electron precipitation

10.1016/j.asr.2024.03.010

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Depletions of Multi‐MeV Electrons and Their Association to Minima in Phase Space Density

Geophysical Research Letters (2022)

Alexander Drozdov Hayley Allison Yuri Shprits Maria Usanova A. Saikin

Fast-localized electron loss, resulting from interactions with electromagnetic ion cyclotron (EMIC) waves, can produce deepening minima in phase space density (PSD) radial profiles. Here, we perform a statistical analysis of local PSD minima to quantify how readily these are associated with radiation belt depletions. The statistics of PSD minima observed over a year are compared to the Versatile Electron Radiation Belts (VERB) simulations, both including and excluding EMIC waves. The observed minima distribution can only be achieved in the simulation including EMIC waves, indicating their importance in the dynamics of the radiation belts. By analyzing electron flux depletions in conjunction with the observed PSD minima, we show that, in the heart of the outer radiation belt (L* < 5), on average, 53% of multi-MeV electron depletions are associated with PSD minima, demonstrating that fast localized loss by interactions with EMIC waves are a common and crucial process for ultra-relativistic electron populations.

Maxima and minima

Van Allen Probes

Emic and etic

10.1029/2021gl097620

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Citations (27)

Assessing the consistency of data-driven whistler mode hiss wave scattering effects during storm-recovery via dedicated error metrics

AGU Fall Meeting Abstracts (2018)

V. Loridan J.‐F. Ripoll M. H. Denton O. Santolı́k S. A. Thaller

Hiss

Whistler

Mode (computer interface)

Source

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The Role of Local Acceleration and Radial Diffusion in Multi‐MeV Electron Flux Enhancements

Journal of Geophysical Research Space Physics (2025)

A. Saikin Alexander Drozdov A. N. Jaynes Dmitri Kondrashov A. J. Boyd

Abstract During the Van Allen Probes era, several multi‐MeV (>4 MeV) electron flux enhancements were observed. The cause of electron acceleration up to multi‐MeV remains an ongoing science topic. In this study, we focus on examining the relationship between phase space density (PSD) radial profile shapes and the occurrence of multi‐MeV electron flux enhancement events. This will determine which process (local acceleration or radial diffusion) is dominant in producing multi‐MeV electron flux enhancements at a specific L*. Growing peaks in PSD radial profiles are associated with the local acceleration (i.e., a wave‐particle interaction) of multi‐MeV electrons. For each growing peak in PSD, we determined the L* where the local acceleration occurs for each respective electron energy. Similarly, we also identify which PSD profiles are related to acceleration via radial diffusion profiles. Both sets of profiles are compared with the Van Allen Probe‐A observed multi‐MeV electron flux enhancements. Results show that both mechanisms (local acceleration and radial diffusion) can facilitate multi‐MeV electron acceleration, however each mechanism has a preferable L* region where it is the dominant acceleration process.

10.1029/2024ja033180

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Data‐Driven Discovery of Fokker‐Planck Equation for the Earth's Radiation Belts Electrons Using Physics‐Informed Neural Networks

Journal of Geophysical Research Space Physics (2022)

Enrico Camporeale George Wilkie Alexander Drozdov Jacob Bortnik

Abstract We use the framework of Physics‐Informed Neural Network (PINN) to solve the inverse problem associated with the Fokker‐Planck equation for radiation belts' electron transport, using 4 years of Van Allen Probes data. Traditionally, reduced models have employed a diffusion equation based on the quasilinear approximation. We show that the dynamics of “killer electrons” is described more accurately by a drift‐diffusion equation, and that drift is as important as diffusion for nearly‐equatorially trapped ∼1 MeV electrons in the inner part of the belt. Moreover, we present a recipe for gleaning physical insight from solving the ill‐posed inverse problem of inferring model coefficients from data using PINNs. Furthermore, we derive a parameterization for the diffusion and drift coefficients as a function of L only, which is both simpler and more accurate than earlier models. Finally, we use the PINN technique to develop an automatic event identification method that allows identifying times at which the radial transport assumption is inadequate to describe all the physics of interest.

Physical law

Heavy traffic approximation

10.1029/2022ja030377

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Citations (18)

Distribution of Seed Electron Phase Space Density Minima in Earth's Radiation Belts

Geophysical Research Letters (2024)

Alexander Drozdov Hayley Allison A. Saikin Q. Schiller Dedong Wang

Abstract We conducted a statistical analysis of local phase space density (PSD) minima across a wide energy range (∼20 keVs to ∼10 MeV), using observations from the Van Allen Probes and the Geostationary Operational Environmental Satellite. We identified deepening minima in PSD profiles of multi‐MeV (∼5% occurrence) and of “seed” electrons (up to 15% occurrence, corresponding to ∼70–100 s keV) and compared their distribution with a 3D diffusion model using the Versatile Electron Radiation Belts (VERB) code. The comparison of the observed and modeled distributions suggests that the PSD minima of seed electrons are likely associated with hiss waves and the corresponding L ‐shell dependent electron lifetimes. However, the observed distribution was not fully reproduced by the model, potentially indicating other fast loss mechanisms of seed electrons.

Maxima and minima

10.1029/2023gl108028

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Citations (3)