Bibliography



Found 29 entries in the Bibliography.


Showing entries from 1 through 29


2021

Reconstructing the dynamics of the outer electron radiation belt by means of the standard and ensemble Kalman filter with the VERB-3D code

Abstract Reconstruction and prediction of the state of the near-Earth space environment is important for anomaly analysis, development of empirical models and understanding of physical processes. Accurate reanalysis or predictions that account for uncertainties in the associated model and the observations, can be obtained by means of data assimilation. The ensemble Kalman filter (EnKF) is one of the most promising filtering tools for non-linear and high dimensional systems in the context of terrestrial weather prediction. In ...

Tibocha, A.; de Wiljes, J.; . Y. Shprits, Y; Aseev, N.;

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002672

Kalman Filter; Ensemble Kalman filter; forecasting; Van Allen Probes

A Comparison of Radial Diffusion Coefficients in 1-D and 3-D Long-Term Radiation Belt Simulations

AbstractRadial diffusion is one of the dominant physical mechanisms driving acceleration and loss of radiation belt electrons. A number of parameterizations for radial diffusion coefficients have been developed, each differing in the dataset used. Here, we investigate the performance of different parameterizations by Brautigam and Albert (2000), Brautigam et al. (2005), Ozeke et al. (2014), Ali et al. (2015); Ali et al. (2016); Ali (2016), and Liu et al. (2016) on long-term radiation belt modeling using the Versatile El ...

. Y. Drozdov, A; Allison, H.; . Y. Shprits, Y; Elkington, S.R.; Aseev, N.A.;

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028707

Radiation belts; radial diffusion; VERB code; Van Allen Probes

Reconstruction of the Radiation Belts for Solar Cycles 17 – 24 (1933 – 2017)

AbstractWe present a reconstruction of the dynamics of the radiation belts from Solar Cycles 17 – 24 which allows us to study how radiation belt activity has varied between the different solar cycles. The radiation belt simulations are produced using the Versatile Electron Radiation Belt (VERB)-3D code. The VERB-3D code simulations incorporate radial, energy, and pitch angle diffusion to reproduce the radiation belts. Our simulations use the historical measurements of Kp (available since Solar Cycle 17, i.e., 1933) to mode ...

Saikin, A.; . Y. Shprits, Y; . Y. Drozdov, A; Landis, D.; Zhelavskaya, I.; Cervantes, S.;

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002524

Radiation belts; numerical modeling; Particle acceleration; Magnetosphere: inner; forecasting; Van Allen Probes

A combined neural network- and physics-based approach for modeling plasmasphere dynamics

AbstractIn recent years, feedforward neural networks (NNs) have been successfully applied to reconstruct global plasmasphere dynamics in the equatorial plane. These neural network-based models capture the large-scale dynamics of the plasmasphere, such as plume formation and erosion of the plasmasphere on the nightside. However, their performance depends strongly on the availability of training data. When the data coverage is limited or non-existent, as occurs during geomagnetic storms, the performance of NNs significantly de ...

Zhelavskaya, I.; Aseev, N.; . Y. Shprits, Y;

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028077

plasmasphere; plasma density; neural networks; data assimilation; Kalman Filter; Machine learning; Van Allen Probes

2020

Quantifying the Effects of EMIC Wave Scattering and Magnetopause Shadowing in the Outer Electron Radiation Belt by Means of Data Assimilation

In this study we investigate two distinct loss mechanisms responsible for the rapid dropouts of radiation belt electrons by assimilating data from Van Allen Probes A and B and Geostationary Operational Environmental Satellites (GOES) 13 and 15 into a 3-D diffusion model. In particular, we examine the respective contribution of electromagnetic ion cyclotron (EMIC) wave scattering and magnetopause shadowing for values of the first adiabatic invariant μ ranging from 300 to 3,000 MeV G−1. We inspect the innovation vector ...

Cervantes, S.; . Y. Shprits, Y; Aseev, N.; Allison, H.;

YEAR: 2020     DOI: https://doi.org/10.1029/2020JA028208

data assimilation; EMIC waves; magnetopause shadowing; innovation vector; Kalman Filter; radiation belt losses; Van Allen Probes

The Role of Hiss, Chorus, and EMIC Waves in the Modeling of the Dynamics of the Multi-MeV Radiation Belt Electrons

In this study, we performed a series of long-term and individual storm simulations with and without hiss, chorus, and electromagnetic ion cyclotron (EMIC) waves. We compared simulation results incorporating different wave modes with Van Allen Probes flux observations to illustrate how hiss and chorus waves aid EMIC waves in depleting multi-MeV electrons. We found that EMIC, hiss, and chorus waves are required to reproduce satellite measurements in our simulations. Our results indicate that hiss waves play a dominant role in ...

. Y. Drozdov, A; Usanova, M.; Hudson, M.; Allison, H.; . Y. Shprits, Y;

YEAR: 2020     DOI: https://doi.org/10.1029/2020JA028282

EMIC waves; Radiation belts; Whistler waves; VERB code; Fokker-Planck diffusion equation; Van Allen Probes

2019

Storm Time Depletions of Multi-MeV Radiation Belt Electrons Observed at Different Pitch Angles

During geomagnetic storms, the rapid depletion of the high-energy (several MeV) outer radiation belt electrons is the result of loss to the interplanetary medium through the magnetopause, outward radial diffusion, and loss to the atmosphere due to wave-particle interactions. We have performed a statistical study of 110 storms using pitch angle resolved electron flux measurements from the Van Allen Probes mission and found that inside of the radiation belt (L* = 3 - 5) the number of storms that result in depletion of electron ...

. Y. Drozdov, A; Aseev, N.; Effenberger, F.; Turner, D.; Saikin, A.; . Y. Shprits, Y;

YEAR: 2019     DOI: 10.1029/2019JA027332

EMIC waves; multi-MeV electrons; Radiation belts; Van Allen Probes

Reanalysis of Ring Current Electron Phase Space Densities Using Van Allen Probe Observations, Convection Model, and Log-Normal Kalman Filter

Aseev, N.; . Y. Shprits, Y;

YEAR: 2019     DOI: 10.1029/2018SW002110

data assimilation; inner magnetosphere; Kalman Filter; Reanalysis; ring current; Van Allen Probes

Electron intensity measurements by the Cluster/RAPID/IES instrument in Earth\textquoterights radiation belts and ring current

The Cluster mission, launched in 2000, has produced a large database of electron flux intensity measurements in the Earth\textquoterights magnetosphere by the Research with Adaptive Particle Imaging Detector (RAPID)/ Imaging Electron Spectrometer (IES) instrument. However, due to background contamination of the data with high-energy electrons (<400 keV) and inner-zone protons (230-630 keV) in the radiation belts and ring current, the data have been rarely used for inner-magnetospheric science. The current paper presents two ...

Smirnov, A.; Kronberg, E.; Latallerie, F.; Daly, P.; Aseev, N.; . Y. Shprits, Y; Kellerman, A.; Kasahara, S.; Turner, D.; Taylor, M.;

YEAR: 2019     DOI: 10.1029/2018SW001989

electrons; Radiation belts; Solar Cycle; Space weather; Van Allen Probes

2018

Observations and Fokker-Planck simulations of the L-shell, energy, and pitch-angle structure of Earth\textquoterights electron radiation belts during quiet times

The evolution of the radiation belts in L-shell (L), energy (E), and equatorial pitch-angle (α0) is analyzed during the calm 11-day interval (March 4 \textendashMarch 15) following the March 1 storm 2013. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker-Planck simulations combined with consistent event-driven scattering modeling from whistler mode hiss waves. Three (L, E, α0)-regions persist through 11 days of hiss wave scattering; the pitch-angle ...

Ripoll, -F.; Loridan, V.; Denton, M.; Cunningham, G.; Reeves, G.; ik, O.; Fennell, J.; Turner, D.; . Y. Drozdov, A; Villa, J.; . Y. Shprits, Y; Thaller, S.; Kurth, W.; Kletzing, C.; Henderson, M.; . Y. Ukhorskiy, A;

YEAR: 2018     DOI: 10.1029/2018JA026111

electron lifetime; hiss waves; pitch-angle diffusion coefficient; Radiation belts; Van Allen Probes; wave particle interactions

2017

Signatures of Ultrarelativistic Electron Loss in the Heart of the Outer Radiation Belt Measured by Van Allen Probes

Up until recently, signatures of the ultrarelativistic electron loss driven by electromagnetic ion cyclotron (EMIC) waves in the Earth\textquoterights outer radiation belt have been limited to direct or indirect measurements of electron precipitation or the narrowing of normalized pitch angle distributions in the heart of the belt. In this study, we demonstrate additional observational evidence of ultrarelativistic electron loss that can be driven by resonant interaction with EMIC waves. We analyzed the profiles derived from ...

Aseev, N.; . Y. Shprits, Y; . Y. Drozdov, A; Kellerman, A.; Usanova, M.; Wang, D.; Zhelavskaya, I.;

YEAR: 2017     DOI: 10.1002/2017JA024485

electron loss; EMIC waves; Radiation belts; ultrarelativistic electrons; Van Allen Probes; wave-particle interactions

EMIC wave parameterization in the long-term VERB code simulation

Electromagnetic ion cyclotron (EMIC) waves play an important role in the dynamics of ultrarelativistic electron population in the radiation belts. However, as EMIC waves are very sporadic, developing a parameterization of such wave properties is a challenging task. Currently, there are no dynamic, activity-dependent models of EMIC waves that can be used in the long-term (several months) simulations, which makes the quantitative modeling of the radiation belt dynamics incomplete. In this study, we investigate Kp, Dst, and AE ...

. Y. Drozdov, A; . Y. Shprits, Y; Usanova, M.; Aseev, N.; Kellerman, A.; Zhu, H.;

YEAR: 2017     DOI: 10.1002/2017JA024389

EMIC; Radiation belts; Van Allen Probes; VERB code

Dependence of radiation belt simulations to assumed radial diffusion rates tested for two empirical models of radial transport

Radial diffusion is one of the dominant physical mechanisms that drives acceleration and loss of the radiation belt electrons, which makes it very important for nowcasting and forecasting space weather models. We investigate the sensitivity of the two parameterizations of the radial diffusion of Brautigam and Albert (2000) and Ozeke et al. (2014) on long-term radiation belt modeling using the Versatile Electron Radiation Belt (VERB). Following Brautigam and Albert (2000) and Ozeke et al. (2014), we first perform 1-D radial d ...

. Y. Drozdov, A; . Y. Shprits, Y; Aseev, N.; Kellerman, A.; Reeves, G.;

YEAR: 2017     DOI: 10.1002/swe.v15.110.1002/2016SW001426

radial diffusion; Radiation belts; Van Allen Probes; VERB code

2016

On the Time Needed to Reach an Equilibrium Structure of the Radiation Belts

In this study, we complement the notion of equilibrium states of the radiation belts with a discussion on the dynamics and time needed to reach equilibrium. We solve for the equilibrium states obtained using 1D radial diffusion with recently developed hiss and chorus lifetimes at constant values of Kp = 1, 3 and 6. We find that the equilibrium states at moderately low Kp, when plotted vs L-shell (L) and energy (E), display the same interesting S-shape for the inner edge of the outer belt as recently observed by the Van Allen ...

Ripoll, J.; Loridan, V.; Cunningham, G.; Reeves, G.; . Y. Shprits, Y;

YEAR: 2016     DOI: 10.1002/2015JA022207

Radiation belts; Van Allen Probes

Automated determination of electron density from electric field measurements on the Van Allen Probes spacecraft

We present the Neural-network-based Upper hybrid Resonance Determination (NURD) algorithm for automatic inference of the electron number density from plasma wave measurements made on board NASA\textquoterights Van Allen Probes mission. A feedforward neural network is developed to determine the upper hybrid resonance frequency, fuhr, from electric field measurements, which is then used to calculate the electron number density. In previous missions, the plasma resonance bands were manually identified, and there have been few a ...

Zhelavskaya, I.; Spasojevic, M.; . Y. Shprits, Y; Kurth, W.;

YEAR: 2016     DOI: 10.1002/2015JA022132

electron number density; neural networks; Van Allen Probes

2015

Global and comprehensive analysis of the inner magnetosphere as a coupled system: Physical understanding and applications

The third Inner Magnetosphere Coupling (IMC III) workshop was held March 2015 at University of California, Los Angeles. The workshop included extensive discussion of space weather and applications bring together scientists from the solar wind, magnetosphere and ionospheric communities as well as space weather stakeholders and researchers focusing on translational research and applications in industry.

. Y. Shprits, Y; Spasojevic, M.;

YEAR: 2015     DOI: 10.1002/2015SW001295

inner magnetosphere; Space weather; workshop

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

In this study, we compare long-term simulations performed by the Versatile Electron Radiation Belt (VERB) code with observations from the MagEIS and REPT 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 ultra-relativistic (>2 MeV) electrons. One year of relativistic electron measurements (μ=700 MeV/G) from October 1, 2012 to O ...

. Y. Drozdov, A; . Y. Shprits, Y; Orlova, K.G.; Kellerman, A.; Subbotin, D.; Baker, D.; Spence, H.E.;

YEAR: 2015     DOI: 10.1002/2014JA020637

EMIC waves; Long-term simulation; Van Allen Probes; VERB code

2014

Characterization of the energy-dependent response of riometer absorption

Ground based riometers provide an inexpensive means to continuously remote sense the precipitation of electrons in the dynamic auroral region of Earth\textquoterights ionosphere. The energy-dependent relationship between riometer absorption and precipitating electrons is thus of great importance for understanding the loss of electrons from the Earth\textquoterights magnetosphere. In this study, statistical and event-based analyses are applied to determine the energy of electrons to which riometers chiefly respond. Time-lagge ...

Kellerman, A.; . Y. Shprits, Y; Makarevich, R.; Spanswick, E.; Donovan, E.; Reeves, G.;

YEAR: 2014     DOI: 10.1002/2014JA020027

cosmic noise absorption; electron energy; particle modeling; Radiation belts; riometer; electron precipitation

Simulation of high-energy radiation belt electron fluxes using NARMAX-VERB coupled codes

This study presents a fusion of data-driven and physics-driven methodologies of energetic electron flux forecasting in the outer radiation belt. Data-driven NARMAX (Nonlinear AutoRegressive Moving Averages with eXogenous inputs) model predictions for geosynchronous orbit fluxes have been used as an outer boundary condition to drive the physics-based Versatile Electron Radiation Belt (VERB) code, to simulate energetic electron fluxes in the outer radiation belt environment. The coupled system has been tested for three extende ...

Pakhotin, I.; . Y. Drozdov, A; . Y. Shprits, Y; Boynton, R.; Subbotin, D.; Balikhin, M.;

YEAR: 2014     DOI: 10.1002/2014JA020238

Radiation belts; Space weather

Survey analysis of chorus intensity at Saturn

In order to conduct theoretical studies or modeling of pitch angle scattering of electrons by whistler mode chorus emission at Saturn, a knowledge of chorus occurrence and magnetic intensity levels, PB, as well as the distribution of PB relative to frequency and spatial parameters is essential. In this paper an extensive survey of whistler mode magnetic intensity levels at Saturn is carried out, and Gaussian fits of PB are performed. We fit the spectrum of wave magnetic intensity between the lower hybrid frequency and fceq/2 ...

Menietti, J.; Averkamp, T.; Groene, J.; Horne, R.; . Y. Shprits, Y; Woodfield, E.; Hospodarsky, G.; Gurnett, D.;

YEAR: 2014     DOI: 10.1002/jgra.v119.1010.1002/2014JA020523

Space physics

Gradual diffusion and punctuated phase space density enhancements of highly relativistic electrons: Van Allen Probes observations

The dual-spacecraft Van Allen Probes mission has provided a new window into mega electron volt (MeV) particle dynamics in the Earth\textquoterights radiation belts. Observations (up to E ~10 MeV) show clearly the behavior of the outer electron radiation belt at different timescales: months-long periods of gradual inward radial diffusive transport and weak loss being punctuated by dramatic flux changes driven by strong solar wind transient events. We present analysis of multi-MeV electron flux and phase space density (PSD) ch ...

Baker, D.; Jaynes, A.; Li, X.; Henderson, M.; Kanekal, S.; Reeves, G.; Spence, H.; Claudepierre, S.; Fennell, J.; Hudson, M.; Thorne, R.; Foster, J.; Erickson, P.; Malaspina, D.; Wygant, J.; Boyd, A.; Kletzing, C.; Drozdov, A.; . Y. Shprits, Y;

YEAR: 2014     DOI: 10.1002/2013GL058942

Van Allen Probes

Prompt energization of relativistic and highly relativistic electrons during a substorm interval: Van Allen Probes observations

On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50\% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes ...

Foster, J.; Erickson, P.; Baker, D.; Claudepierre, S.; Kletzing, C.; Kurth, W.; Reeves, G.; Thaller, S.; Spence, H.; . Y. Shprits, Y; Wygant, J.;

YEAR: 2014     DOI: 10.1002/2013GL058438

Van Allen Probes

2013

Scattering rates of inner belt protons by EMIC waves: A comparison between test particle and diffusion simulations

Inner belt energetic protons are a hindrance to development of space technologies. The emission of electromagnetic ion cyclotron (EMIC) waves from spaceborne transmitters has been proposed as a way to solve this problem. The interaction between particles and narrowband emissions has been typically studied using nonlinear test particle simulations. We show that this formulation results in a random walk of the inner belt protons in velocity space. In this paper we compute bounce-averaged pitch angle diffusion rates from test p ...

de Soria-Santacruz, M.; Orlova, K.; Martinez-Sanchez, M.; . Y. Shprits, Y;

YEAR: 2013     DOI: 10.1002/grl.50925

EMIC; inner belt; wave-particle interactions

2007

Dynamic evolution of energetic outer zone electrons due to wave-particle interactions during storms

[1] Relativistic electrons in the outer radiation belt are subjected to pitch angle and energy diffusion by chorus, electromagnetic ion cyclotron (EMIC), and hiss waves. Using quasi-linear diffusion coefficients for cyclotron resonance with field-aligned waves, we examine whether the resonant interactions with chorus waves produce a net acceleration or loss of relativistic electrons. We also examine the effect of pitch angle scattering by EMIC and hiss waves during the main and recovery phases of a storm. The numerical simul ...

Li, W.; . Y. Shprits, Y; Thorne, R.;

YEAR: 2007     DOI: 10.1029/2007JA012368

Local Loss due to VLF/ELF/EMIC Waves

Refilling of the slot region between the inner and outer electron radiation belts during geomagnetic storms

[1] Energetic electrons (>=50 keV) are injected into the slot region (2 < L < 4) between the inner and outer radiation belts during the early recovery phase of geomagnetic storms. Enhanced convection from the plasma sheet can account for the storm-time injection at lower energies but does not explain the rapid appearance of higher-energy electrons (>=150 keV). The effectiveness of either radial diffusion (driven by enhanced ULF waves) or local acceleration (during interactions with enhanced whistler mode chorus emissions), a ...

Thorne, R.; . Y. Shprits, Y; Meredith, N.; Horne, R.; Li, W.; Lyons, L.;

YEAR: 2007     DOI: 10.1029/2006JA012176

Shock-Induced Transport. Slot Refilling and Formation of New Belts.

2006

Observation of two distinct, rapid loss mechanisms during the 20 November 2003 radiation belt dropout event

The relativistic electron dropout event on 20 November 2003 is studied using data from a number of satellites including SAMPEX, HEO, ACE, POES, and FAST. The observations suggest that the dropout may have been caused by two separate mechanisms that operate at high and low L-shells, respectively, with a separation at L \~ 5. At high L-shells (L > 5), the dropout is approximately independent of energy and consistent with losses to the magnetopause aided by the Dst effect and outward radial diffusion which can deplete relativis ...

Bortnik, J.; Thorne, R.; O\textquoterightBrien, T.; Green, J.; Strangeway, R.; . Y. Shprits, Y; Baker, D.;

YEAR: 2006     DOI: 10.1029/2006JA011802

Local Loss due to VLF/ELF/EMIC Waves

Outward radial diffusion driven by losses at magnetopause

Loss mechanisms responsible for the sudden depletions of the outer electron radiation belt are examined based on observations and radial diffusion modeling, with L*-derived boundary conditions. SAMPEX data for October\textendashDecember 2003 indicate that depletions often occur when the magnetopause is compressed and geomagnetic activity is high, consistent with outward radial diffusion for L* > 4 driven by loss to the magnetopause. Multichannel Highly Elliptical Orbit (HEO) satellite observations show that depletions at hig ...

. Y. Shprits, Y; Thorne, R.; Friedel, R.; Reeves, G.; Fennell, J.; Baker, D.; Kanekal, S.;

YEAR: 2006     DOI: 10.1029/2006JA011657

Magnetopause Losses

2005

Timescale for MeV electron microburst loss during geomagnetic storms

Energetic electrons in the outer radiation belt can resonate with intense bursts of whistler-mode chorus emission leading to microburst precipitation into the atmosphere. The timescale for removal of outer zone MeV electrons during the main phase of the October 1998 magnetic storm has been computed by comparing the rate of microburst loss observed on SAMPEX with trapped flux levels observed on Polar. Effective lifetimes are comparable to a day and are relatively independent of L shell. The lifetimes have also been evaluated ...

Thorne, R.; O\textquoterightBrien, T.; . Y. Shprits, Y; Summers, D.; Horne, R.;

YEAR: 2005     DOI: 10.1029/2004JA010882

Local Loss due to VLF/ELF/EMIC Waves

2004

Time dependent radial diffusion modeling of relativistic electrons with realistic loss rates

Model simulations are compared to the typically observed evolution of MeV electron fluxes during geomagnetic storms to investigate whether radial diffusion alone can account for the observed variability and to estimate the effect of electron lifetimes. We demonstrate that knowledge of lifetimes is crucial for understanding the radial structure of the storm-time radiation belts and their temporal evolution. Our model results suggest that outer zone lifetimes at 1 MeV are on the order of few days during quite-times and less th ...

. Y. Shprits, Y; Thorne, R.;

YEAR: 2004     DOI: 10.1029/2004GL019591

Radial Transport



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