Bibliography

Modeling the Dynamics of Radiation Belt Electrons with Source and Loss Driven by the Solar Wind

Abstract A radial diffusion model directly driven by the solar wind is developed to reproduce MeV electron variations between L=2-12 (L is L* in this study) from October 2012 to April 2015. The radial diffusion coefficient, internal source rate, quick loss due to EMIC waves, and slow loss due to hiss waves are all expressed in terms of the solar wind speed, dynamic pressure, and interplanetary magnetic field (IMF). The model achieves a prediction efficiency (PE) of 0.45 at L=5 and 0.51 at L=4 after converting the electron phase space densities to differential fluxes and comparing with Van Allen Probes measurements of 2 MeV and 3 MeV electrons at L=5 and L=4, respectively. Machine learning techniques are used to tune parameters to get higher PE. By tuning parameters for every 60-day period, the model obtains PE values of 0.58 and 0.82 at L=5 and L=4, respectively. Inspired by these results, we divide the solar wind activity into three categories based on the condition of solar wind speed, IMF Bz, and dynamic pressure, and then tune these three sets of parameters to obtain the highest PE. This experiment confirms that the solar wind speed has the greatest influence on the electron flux variations, particularly at higher L, while the dynamic pressure has more influence at lower L. Also, the PE at L=4 is mostly higher than those at L=5, suggesting that the electron loss due to the magnetopause shadowing combined with the outward radial diffusion is not well captured in the model. This article is protected by copyright. All rights reserved.

Xiang, Zheng; Li, Xinlin; Kapali, Sudha; Gannon, Jennifer; Ni, Binbin; Zhao, Hong; Zhang, Kun; Khoo, Leng;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028988

Radiation belt; Solar wind; flux prediction; radial diffusion; magnetopause shadowing; wave-particle interactions; Van Allen Probes

Modeling the Dynamics of Radiation Belt Electrons with Source and Loss Driven by the Solar Wind

Abstract A radial diffusion model directly driven by the solar wind is developed to reproduce MeV electron variations between L=2-12 (L is L* in this study) from October 2012 to April 2015. The radial diffusion coefficient, internal source rate, quick loss due to EMIC waves, and slow loss due to hiss waves are all expressed in terms of the solar wind speed, dynamic pressure, and interplanetary magnetic field (IMF). The model achieves a prediction efficiency (PE) of 0.45 at L=5 and 0.51 at L=4 after converting the electron phase space densities to differential fluxes and comparing with Van Allen Probes measurements of 2 MeV and 3 MeV electrons at L=5 and L=4, respectively. Machine learning techniques are used to tune parameters to get higher PE. By tuning parameters for every 60-day period, the model obtains PE values of 0.58 and 0.82 at L=5 and L=4, respectively. Inspired by these results, we divide the solar wind activity into three categories based on the condition of solar wind speed, IMF Bz, and dynamic pressure, and then tune these three sets of parameters to obtain the highest PE. This experiment confirms that the solar wind speed has the greatest influence on the electron flux variations, particularly at higher L, while the dynamic pressure has more influence at lower L. Also, the PE at L=4 is mostly higher than those at L=5, suggesting that the electron loss due to the magnetopause shadowing combined with the outward radial diffusion is not well captured in the model. This article is protected by copyright. All rights reserved.

Xiang, Zheng; Li, Xinlin; Kapali, Sudha; Gannon, Jennifer; Ni, Binbin; Zhao, Hong; Zhang, Kun; Khoo, Leng;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028988

Radiation belt; Solar wind; flux prediction; radial diffusion; magnetopause shadowing; wave-particle interactions; Van Allen Probes

Modeling the Dynamics of Radiation Belt Electrons with Source and Loss Driven by the Solar Wind

Abstract A radial diffusion model directly driven by the solar wind is developed to reproduce MeV electron variations between L=2-12 (L is L* in this study) from October 2012 to April 2015. The radial diffusion coefficient, internal source rate, quick loss due to EMIC waves, and slow loss due to hiss waves are all expressed in terms of the solar wind speed, dynamic pressure, and interplanetary magnetic field (IMF). The model achieves a prediction efficiency (PE) of 0.45 at L=5 and 0.51 at L=4 after converting the electron phase space densities to differential fluxes and comparing with Van Allen Probes measurements of 2 MeV and 3 MeV electrons at L=5 and L=4, respectively. Machine learning techniques are used to tune parameters to get higher PE. By tuning parameters for every 60-day period, the model obtains PE values of 0.58 and 0.82 at L=5 and L=4, respectively. Inspired by these results, we divide the solar wind activity into three categories based on the condition of solar wind speed, IMF Bz, and dynamic pressure, and then tune these three sets of parameters to obtain the highest PE. This experiment confirms that the solar wind speed has the greatest influence on the electron flux variations, particularly at higher L, while the dynamic pressure has more influence at lower L. Also, the PE at L=4 is mostly higher than those at L=5, suggesting that the electron loss due to the magnetopause shadowing combined with the outward radial diffusion is not well captured in the model. This article is protected by copyright. All rights reserved.

Xiang, Zheng; Li, Xinlin; Kapali, Sudha; Gannon, Jennifer; Ni, Binbin; Zhao, Hong; Zhang, Kun; Khoo, Leng;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028988

Radiation belt; Solar wind; flux prediction; radial diffusion; magnetopause shadowing; wave-particle interactions; Van Allen Probes

Modeling the Dynamics of Radiation Belt Electrons with Source and Loss Driven by the Solar Wind

Abstract A radial diffusion model directly driven by the solar wind is developed to reproduce MeV electron variations between L=2-12 (L is L* in this study) from October 2012 to April 2015. The radial diffusion coefficient, internal source rate, quick loss due to EMIC waves, and slow loss due to hiss waves are all expressed in terms of the solar wind speed, dynamic pressure, and interplanetary magnetic field (IMF). The model achieves a prediction efficiency (PE) of 0.45 at L=5 and 0.51 at L=4 after converting the electron phase space densities to differential fluxes and comparing with Van Allen Probes measurements of 2 MeV and 3 MeV electrons at L=5 and L=4, respectively. Machine learning techniques are used to tune parameters to get higher PE. By tuning parameters for every 60-day period, the model obtains PE values of 0.58 and 0.82 at L=5 and L=4, respectively. Inspired by these results, we divide the solar wind activity into three categories based on the condition of solar wind speed, IMF Bz, and dynamic pressure, and then tune these three sets of parameters to obtain the highest PE. This experiment confirms that the solar wind speed has the greatest influence on the electron flux variations, particularly at higher L, while the dynamic pressure has more influence at lower L. Also, the PE at L=4 is mostly higher than those at L=5, suggesting that the electron loss due to the magnetopause shadowing combined with the outward radial diffusion is not well captured in the model. This article is protected by copyright. All rights reserved.

Xiang, Zheng; Li, Xinlin; Kapali, Sudha; Gannon, Jennifer; Ni, Binbin; Zhao, Hong; Zhang, Kun; Khoo, Leng;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028988

Radiation belt; Solar wind; flux prediction; radial diffusion; magnetopause shadowing; wave-particle interactions; Van Allen Probes

Observations and simulations of dropout events and flux decays in October 2013: Comparing MEO equatorial with LEO polar orbit

Abstract We compare ESA PROBA-V observations of electron flux at LEO with those from the NASA Van Allen Probes mostly at MEO for October 2013. Dropouts are visible at all energy during 4 storms from both satellites. Equatorial trapped electron fluxes are higher than at LEO by 102 (<1 MeV) to 105 (>2.5 MeV). We observe a quite isotropic structure of the outer belt during quiet times, contrary to the inner belt, and pitch angle dependence of high energy injection. We find very good overlap of the outer belt at MEO and LEO at ∼0.5 MeV. We use test-particle simulations of the energetic electrons trapped in the terrestrial magnetic field to study the outer radiation belt electron flux changes during geomagnetic storms. We show that the Dst (Disturbance storm time) effect during the main phase of a geomagnetic storm results in a betatron mechanism causing outward radial drift and a deceleration of the electrons. This outward drift motion is energy independent, pitch angle dependent, and represent a significant distance (∼1 L-shell at L=5 for moderate storms). At fixed L-shell, this causes a decay of the LEO precipitating flux (adiabatic outward motion), followed by a return to the normal state (adiabatic inward motion) during main and recovery phases. Dst effect, associated with magnetopause shadowing and radial diffusion can explain the main characteristics of outer radiation belt electron dropouts in October 2013. We also use Fokker-Planck simulations with event-driven diffusion coefficients at high temporal resolution, in order to distinguish instantaneous loss from the gradual scattering that depopulates the slot region and the outer belt after storms. Simulations reproduce the slot formation and the gradual loss in the outer belt. The typical energy-dependence of these losses leads to the absence of scattering for relativistic and ultra-relativistic electrons in the outer belt, oppositely to dropouts.

Pierrard, V.; Ripoll, J.-F.; Cunningham, G.; Botek, E.; Santolik, O.; Thaller, S.; Kurth, W.; Cosmides, M.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028850

Radiation belts; relativistic electrons; Geomagnetic storms; energetic particles; Van Allen Probes

Observations and simulations of dropout events and flux decays in October 2013: Comparing MEO equatorial with LEO polar orbit

Abstract We compare ESA PROBA-V observations of electron flux at LEO with those from the NASA Van Allen Probes mostly at MEO for October 2013. Dropouts are visible at all energy during 4 storms from both satellites. Equatorial trapped electron fluxes are higher than at LEO by 102 (<1 MeV) to 105 (>2.5 MeV). We observe a quite isotropic structure of the outer belt during quiet times, contrary to the inner belt, and pitch angle dependence of high energy injection. We find very good overlap of the outer belt at MEO and LEO at ∼0.5 MeV. We use test-particle simulations of the energetic electrons trapped in the terrestrial magnetic field to study the outer radiation belt electron flux changes during geomagnetic storms. We show that the Dst (Disturbance storm time) effect during the main phase of a geomagnetic storm results in a betatron mechanism causing outward radial drift and a deceleration of the electrons. This outward drift motion is energy independent, pitch angle dependent, and represent a significant distance (∼1 L-shell at L=5 for moderate storms). At fixed L-shell, this causes a decay of the LEO precipitating flux (adiabatic outward motion), followed by a return to the normal state (adiabatic inward motion) during main and recovery phases. Dst effect, associated with magnetopause shadowing and radial diffusion can explain the main characteristics of outer radiation belt electron dropouts in October 2013. We also use Fokker-Planck simulations with event-driven diffusion coefficients at high temporal resolution, in order to distinguish instantaneous loss from the gradual scattering that depopulates the slot region and the outer belt after storms. Simulations reproduce the slot formation and the gradual loss in the outer belt. The typical energy-dependence of these losses leads to the absence of scattering for relativistic and ultra-relativistic electrons in the outer belt, oppositely to dropouts.

Pierrard, V.; Ripoll, J.-F.; Cunningham, G.; Botek, E.; Santolik, O.; Thaller, S.; Kurth, W.; Cosmides, M.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028850

Radiation belts; relativistic electrons; Geomagnetic storms; energetic particles; Van Allen Probes

Observations and simulations of dropout events and flux decays in October 2013: Comparing MEO equatorial with LEO polar orbit

Abstract We compare ESA PROBA-V observations of electron flux at LEO with those from the NASA Van Allen Probes mostly at MEO for October 2013. Dropouts are visible at all energy during 4 storms from both satellites. Equatorial trapped electron fluxes are higher than at LEO by 102 (<1 MeV) to 105 (>2.5 MeV). We observe a quite isotropic structure of the outer belt during quiet times, contrary to the inner belt, and pitch angle dependence of high energy injection. We find very good overlap of the outer belt at MEO and LEO at ∼0.5 MeV. We use test-particle simulations of the energetic electrons trapped in the terrestrial magnetic field to study the outer radiation belt electron flux changes during geomagnetic storms. We show that the Dst (Disturbance storm time) effect during the main phase of a geomagnetic storm results in a betatron mechanism causing outward radial drift and a deceleration of the electrons. This outward drift motion is energy independent, pitch angle dependent, and represent a significant distance (∼1 L-shell at L=5 for moderate storms). At fixed L-shell, this causes a decay of the LEO precipitating flux (adiabatic outward motion), followed by a return to the normal state (adiabatic inward motion) during main and recovery phases. Dst effect, associated with magnetopause shadowing and radial diffusion can explain the main characteristics of outer radiation belt electron dropouts in October 2013. We also use Fokker-Planck simulations with event-driven diffusion coefficients at high temporal resolution, in order to distinguish instantaneous loss from the gradual scattering that depopulates the slot region and the outer belt after storms. Simulations reproduce the slot formation and the gradual loss in the outer belt. The typical energy-dependence of these losses leads to the absence of scattering for relativistic and ultra-relativistic electrons in the outer belt, oppositely to dropouts.

Pierrard, V.; Ripoll, J.-F.; Cunningham, G.; Botek, E.; Santolik, O.; Thaller, S.; Kurth, W.; Cosmides, M.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028850

Radiation belts; relativistic electrons; Geomagnetic storms; energetic particles; Van Allen Probes

Observations and simulations of dropout events and flux decays in October 2013: Comparing MEO equatorial with LEO polar orbit

Abstract We compare ESA PROBA-V observations of electron flux at LEO with those from the NASA Van Allen Probes mostly at MEO for October 2013. Dropouts are visible at all energy during 4 storms from both satellites. Equatorial trapped electron fluxes are higher than at LEO by 102 (<1 MeV) to 105 (>2.5 MeV). We observe a quite isotropic structure of the outer belt during quiet times, contrary to the inner belt, and pitch angle dependence of high energy injection. We find very good overlap of the outer belt at MEO and LEO at ∼0.5 MeV. We use test-particle simulations of the energetic electrons trapped in the terrestrial magnetic field to study the outer radiation belt electron flux changes during geomagnetic storms. We show that the Dst (Disturbance storm time) effect during the main phase of a geomagnetic storm results in a betatron mechanism causing outward radial drift and a deceleration of the electrons. This outward drift motion is energy independent, pitch angle dependent, and represent a significant distance (∼1 L-shell at L=5 for moderate storms). At fixed L-shell, this causes a decay of the LEO precipitating flux (adiabatic outward motion), followed by a return to the normal state (adiabatic inward motion) during main and recovery phases. Dst effect, associated with magnetopause shadowing and radial diffusion can explain the main characteristics of outer radiation belt electron dropouts in October 2013. We also use Fokker-Planck simulations with event-driven diffusion coefficients at high temporal resolution, in order to distinguish instantaneous loss from the gradual scattering that depopulates the slot region and the outer belt after storms. Simulations reproduce the slot formation and the gradual loss in the outer belt. The typical energy-dependence of these losses leads to the absence of scattering for relativistic and ultra-relativistic electrons in the outer belt, oppositely to dropouts.

Pierrard, V.; Ripoll, J.-F.; Cunningham, G.; Botek, E.; Santolik, O.; Thaller, S.; Kurth, W.; Cosmides, M.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028850

Radiation belts; relativistic electrons; Geomagnetic storms; energetic particles; Van Allen Probes

On the Formation of Phantom Electron Phase Space Density Peaks in Single Spacecraft Radiation Belt Data

Abstract This paper examines the rapid losses and acceleration of trapped relativistic and ultrarelativistic electron populations in the Van Allen radiation belt during the September 7-9, 2017, geomagnetic storm. By analyzing the dynamics of the last closed drift shell (LCDS) and the electron flux and phase space density (PSD), we show that the electron dropouts are consistent with magnetopause shadowing and outward radial diffusion to the compressed LCDS. During the recovery phase an in-bound pass of Van Allen Probe A shows an apparent local peak in PSD, but which does not exist. A careful analysis of the multipoint measurements by the Van Allen Probes reveals instead how the apparent PSD peak arises from aliasing monotonic PSD profiles which are rapidly increasing due to acceleration from very fast inwards radial diffusion. In the absence of such multi-satellite conjunctions during fast acceleration events, such peaks might otherwise be associated with local acceleration processes.

Olifer, L.; Mann, I.; Ozeke, L.; Morley, S.; Louis, H.;

Published by: Geophysical Research Letters      Published on: 05/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020GL092351

Van Allen Probes; magnetopause shadowing; ULF wave radial diffusion; electron phase space density

Characteristics of low-harmonic magnetosonic waves in the Earth’s inner magnetosphere

Abstract Magnetosonic (MS) waves are electromagnetic waves that play important roles in the acceleration and scattering of radiation belt electrons. However, previous statistical analyses of the global MS wave distribution were mainly restricted to magnetic field measurements. In this study, we first report a low-harmonic MS wave event observed only by the electric field instrument of Van Allen Probes. The MS wave frequencies follow the local proton gyrofrequency (fcp), which suggests the characteristics of nearly local generation. We further statistically investigate similar wave events using Van Allen Probes data. The identified MS wave power exhibits peaks between 4fcp and 10fcp, regardless of the L-shell, but it shows a magnetic local time (MLT) dependence. This work is supplemental to previous MS wave frequency spectra and provides new insights to better understand the source region of MS waves in the Earth’s magnetosphere.

Teng, S.; Liu, N.; Ma, Q.; Tao, X.;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL093119

Low-frequency magnetosonic wave; wave generation; Magnetosonic wave spectra; Van Allen Probes

Characteristics of low-harmonic magnetosonic waves in the Earth’s inner magnetosphere

Abstract Magnetosonic (MS) waves are electromagnetic waves that play important roles in the acceleration and scattering of radiation belt electrons. However, previous statistical analyses of the global MS wave distribution were mainly restricted to magnetic field measurements. In this study, we first report a low-harmonic MS wave event observed only by the electric field instrument of Van Allen Probes. The MS wave frequencies follow the local proton gyrofrequency (fcp), which suggests the characteristics of nearly local generation. We further statistically investigate similar wave events using Van Allen Probes data. The identified MS wave power exhibits peaks between 4fcp and 10fcp, regardless of the L-shell, but it shows a magnetic local time (MLT) dependence. This work is supplemental to previous MS wave frequency spectra and provides new insights to better understand the source region of MS waves in the Earth’s magnetosphere.

Teng, S.; Liu, N.; Ma, Q.; Tao, X.;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL093119

Low-frequency magnetosonic wave; wave generation; Magnetosonic wave spectra; Van Allen Probes

A Concise Empirical Formula for the Field-aligned Distribution of Auroral Kilometeric Radiation based on Arase satellite and Van Allen Probes

Abstract Auroral kilometric radiations (AKR) are strong radio emission phenomena, and can prduce significant acceleration or scattering of radiation belt electrons. The variation of AKR wave amplitude with the latitude (λ) has not been reported so far owing to lack of measurements. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study on the AKR electric field amplitude (Et) in the radiation belts for |λ| = 0° − 40° and L-shell L = 3.0−6.2. Results (totally 14,770 samples) show that Et can be described by a concise formula: Et(λ) = E0  exp(ξ sin |λ|), decreasing with decreasing latitude. Fitting parameters E0 and ξ are limited in the ranges: E0 = 0.054−0.340 mV/m and ξ = 3.0−4.2. Wave amplitudes are greater (smaller) under intense (weak) geomagnetic conditions. This study helps to better quantify the gyroresonance between AKR and radiation belt electrons.

Zhang, Sai; Liu, Si; Li, Wentao; He, Yihua; Yang, Qiwu; Xiao, Fuliang; Kumamoto, Atsushi; Miyoshi, Yoshizumi; Nakamura, Yosuke; Tsuchiya, Fuminori; Kasahara, Yoshiya; Shinohara, Iku;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL092805

AKR; wave amplitude; geomagnetic latitude; Radiation belt; field-aligned; Van Allen Probes

A Concise Empirical Formula for the Field-aligned Distribution of Auroral Kilometeric Radiation based on Arase satellite and Van Allen Probes

Abstract Auroral kilometric radiations (AKR) are strong radio emission phenomena, and can prduce significant acceleration or scattering of radiation belt electrons. The variation of AKR wave amplitude with the latitude (λ) has not been reported so far owing to lack of measurements. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study on the AKR electric field amplitude (Et) in the radiation belts for |λ| = 0° − 40° and L-shell L = 3.0−6.2. Results (totally 14,770 samples) show that Et can be described by a concise formula: Et(λ) = E0  exp(ξ sin |λ|), decreasing with decreasing latitude. Fitting parameters E0 and ξ are limited in the ranges: E0 = 0.054−0.340 mV/m and ξ = 3.0−4.2. Wave amplitudes are greater (smaller) under intense (weak) geomagnetic conditions. This study helps to better quantify the gyroresonance between AKR and radiation belt electrons.

Zhang, Sai; Liu, Si; Li, Wentao; He, Yihua; Yang, Qiwu; Xiao, Fuliang; Kumamoto, Atsushi; Miyoshi, Yoshizumi; Nakamura, Yosuke; Tsuchiya, Fuminori; Kasahara, Yoshiya; Shinohara, Iku;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL092805

AKR; wave amplitude; geomagnetic latitude; Radiation belt; field-aligned; Van Allen Probes

A Concise Empirical Formula for the Field-aligned Distribution of Auroral Kilometeric Radiation based on Arase satellite and Van Allen Probes

Abstract Auroral kilometric radiations (AKR) are strong radio emission phenomena, and can prduce significant acceleration or scattering of radiation belt electrons. The variation of AKR wave amplitude with the latitude (λ) has not been reported so far owing to lack of measurements. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study on the AKR electric field amplitude (Et) in the radiation belts for |λ| = 0° − 40° and L-shell L = 3.0−6.2. Results (totally 14,770 samples) show that Et can be described by a concise formula: Et(λ) = E0  exp(ξ sin |λ|), decreasing with decreasing latitude. Fitting parameters E0 and ξ are limited in the ranges: E0 = 0.054−0.340 mV/m and ξ = 3.0−4.2. Wave amplitudes are greater (smaller) under intense (weak) geomagnetic conditions. This study helps to better quantify the gyroresonance between AKR and radiation belt electrons.

Zhang, Sai; Liu, Si; Li, Wentao; He, Yihua; Yang, Qiwu; Xiao, Fuliang; Kumamoto, Atsushi; Miyoshi, Yoshizumi; Nakamura, Yosuke; Tsuchiya, Fuminori; Kasahara, Yoshiya; Shinohara, Iku;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL092805

AKR; wave amplitude; geomagnetic latitude; Radiation belt; field-aligned; Van Allen Probes

A Concise Empirical Formula for the Field-aligned Distribution of Auroral Kilometeric Radiation based on Arase satellite and Van Allen Probes

Abstract Auroral kilometric radiations (AKR) are strong radio emission phenomena, and can prduce significant acceleration or scattering of radiation belt electrons. The variation of AKR wave amplitude with the latitude (λ) has not been reported so far owing to lack of measurements. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study on the AKR electric field amplitude (Et) in the radiation belts for |λ| = 0° − 40° and L-shell L = 3.0−6.2. Results (totally 14,770 samples) show that Et can be described by a concise formula: Et(λ) = E0  exp(ξ sin |λ|), decreasing with decreasing latitude. Fitting parameters E0 and ξ are limited in the ranges: E0 = 0.054−0.340 mV/m and ξ = 3.0−4.2. Wave amplitudes are greater (smaller) under intense (weak) geomagnetic conditions. This study helps to better quantify the gyroresonance between AKR and radiation belt electrons.

Zhang, Sai; Liu, Si; Li, Wentao; He, Yihua; Yang, Qiwu; Xiao, Fuliang; Kumamoto, Atsushi; Miyoshi, Yoshizumi; Nakamura, Yosuke; Tsuchiya, Fuminori; Kasahara, Yoshiya; Shinohara, Iku;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL092805

AKR; wave amplitude; geomagnetic latitude; Radiation belt; field-aligned; Van Allen Probes

A Concise Empirical Formula for the Field-aligned Distribution of Auroral Kilometeric Radiation based on Arase satellite and Van Allen Probes

Abstract Auroral kilometric radiations (AKR) are strong radio emission phenomena, and can prduce significant acceleration or scattering of radiation belt electrons. The variation of AKR wave amplitude with the latitude (λ) has not been reported so far owing to lack of measurements. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study on the AKR electric field amplitude (Et) in the radiation belts for |λ| = 0° − 40° and L-shell L = 3.0−6.2. Results (totally 14,770 samples) show that Et can be described by a concise formula: Et(λ) = E0  exp(ξ sin |λ|), decreasing with decreasing latitude. Fitting parameters E0 and ξ are limited in the ranges: E0 = 0.054−0.340 mV/m and ξ = 3.0−4.2. Wave amplitudes are greater (smaller) under intense (weak) geomagnetic conditions. This study helps to better quantify the gyroresonance between AKR and radiation belt electrons.

Zhang, Sai; Liu, Si; Li, Wentao; He, Yihua; Yang, Qiwu; Xiao, Fuliang; Kumamoto, Atsushi; Miyoshi, Yoshizumi; Nakamura, Yosuke; Tsuchiya, Fuminori; Kasahara, Yoshiya; Shinohara, Iku;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL092805

AKR; wave amplitude; geomagnetic latitude; Radiation belt; field-aligned; Van Allen Probes

A Concise Empirical Formula for the Field-aligned Distribution of Auroral Kilometeric Radiation based on Arase satellite and Van Allen Probes

Abstract Auroral kilometric radiations (AKR) are strong radio emission phenomena, and can prduce significant acceleration or scattering of radiation belt electrons. The variation of AKR wave amplitude with the latitude (λ) has not been reported so far owing to lack of measurements. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study on the AKR electric field amplitude (Et) in the radiation belts for |λ| = 0° − 40° and L-shell L = 3.0−6.2. Results (totally 14,770 samples) show that Et can be described by a concise formula: Et(λ) = E0  exp(ξ sin |λ|), decreasing with decreasing latitude. Fitting parameters E0 and ξ are limited in the ranges: E0 = 0.054−0.340 mV/m and ξ = 3.0−4.2. Wave amplitudes are greater (smaller) under intense (weak) geomagnetic conditions. This study helps to better quantify the gyroresonance between AKR and radiation belt electrons.

Zhang, Sai; Liu, Si; Li, Wentao; He, Yihua; Yang, Qiwu; Xiao, Fuliang; Kumamoto, Atsushi; Miyoshi, Yoshizumi; Nakamura, Yosuke; Tsuchiya, Fuminori; Kasahara, Yoshiya; Shinohara, Iku;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL092805

AKR; wave amplitude; geomagnetic latitude; Radiation belt; field-aligned; Van Allen Probes

A Concise Empirical Formula for the Field-aligned Distribution of Auroral Kilometeric Radiation based on Arase satellite and Van Allen Probes

Abstract Auroral kilometric radiations (AKR) are strong radio emission phenomena, and can prduce significant acceleration or scattering of radiation belt electrons. The variation of AKR wave amplitude with the latitude (λ) has not been reported so far owing to lack of measurements. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study on the AKR electric field amplitude (Et) in the radiation belts for |λ| = 0° − 40° and L-shell L = 3.0−6.2. Results (totally 14,770 samples) show that Et can be described by a concise formula: Et(λ) = E0  exp(ξ sin |λ|), decreasing with decreasing latitude. Fitting parameters E0 and ξ are limited in the ranges: E0 = 0.054−0.340 mV/m and ξ = 3.0−4.2. Wave amplitudes are greater (smaller) under intense (weak) geomagnetic conditions. This study helps to better quantify the gyroresonance between AKR and radiation belt electrons.

Zhang, Sai; Liu, Si; Li, Wentao; He, Yihua; Yang, Qiwu; Xiao, Fuliang; Kumamoto, Atsushi; Miyoshi, Yoshizumi; Nakamura, Yosuke; Tsuchiya, Fuminori; Kasahara, Yoshiya; Shinohara, Iku;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL092805

AKR; wave amplitude; geomagnetic latitude; Radiation belt; field-aligned; Van Allen Probes

A Concise Empirical Formula for the Field-aligned Distribution of Auroral Kilometeric Radiation based on Arase satellite and Van Allen Probes

Abstract Auroral kilometric radiations (AKR) are strong radio emission phenomena, and can prduce significant acceleration or scattering of radiation belt electrons. The variation of AKR wave amplitude with the latitude (λ) has not been reported so far owing to lack of measurements. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study on the AKR electric field amplitude (Et) in the radiation belts for |λ| = 0° − 40° and L-shell L = 3.0−6.2. Results (totally 14,770 samples) show that Et can be described by a concise formula: Et(λ) = E0  exp(ξ sin |λ|), decreasing with decreasing latitude. Fitting parameters E0 and ξ are limited in the ranges: E0 = 0.054−0.340 mV/m and ξ = 3.0−4.2. Wave amplitudes are greater (smaller) under intense (weak) geomagnetic conditions. This study helps to better quantify the gyroresonance between AKR and radiation belt electrons.

Zhang, Sai; Liu, Si; Li, Wentao; He, Yihua; Yang, Qiwu; Xiao, Fuliang; Kumamoto, Atsushi; Miyoshi, Yoshizumi; Nakamura, Yosuke; Tsuchiya, Fuminori; Kasahara, Yoshiya; Shinohara, Iku;

Published by: Geophysical Research Letters      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL092805

AKR; wave amplitude; geomagnetic latitude; Radiation belt; field-aligned; Van Allen Probes

Energetic electron detection packages on board Chinese navigation satellites in MEO

Abstract Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E telescope technology, and a deep dielectric charging monitor (DDCM). The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30° field of view (FOV). The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30° cone-angle FOV. The ground test and calibration results indicate that these three sensors exhibit excellent performance. Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer (MagEIS) of the Van Allen Probes spacecraft, with an average relative deviation of 27.3\% for the energy spectra. The charging currents and voltages measured by the DDCM during storms are consistent with the high-energy electron observations of the HED, demonstrating the effectiveness of the DDCM. The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.

YuGuang, Ye; Hong, Zou; Qiu-Gang, Zong; HongFei, Chen; JiQing, Zou; WeiHong, Shi; XiangQian, Yu; WeiYing, Zhong; YongFu, Wang; YiXin, Hao; ZhiYang, Liu; XiangHong, Jia; Bo, Wang; XiaoPing, Yang; XiaoYun, Hao;

Published by: Earth and Planetary Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.26464/epp2021021

Radiation belts; energetic electron detection; Pin-hole technology; Chinese navigation satellites; MEO; internal charging; Van Allen Probes

Energetic electron detection packages on board Chinese navigation satellites in MEO

Abstract Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E telescope technology, and a deep dielectric charging monitor (DDCM). The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30° field of view (FOV). The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30° cone-angle FOV. The ground test and calibration results indicate that these three sensors exhibit excellent performance. Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer (MagEIS) of the Van Allen Probes spacecraft, with an average relative deviation of 27.3\% for the energy spectra. The charging currents and voltages measured by the DDCM during storms are consistent with the high-energy electron observations of the HED, demonstrating the effectiveness of the DDCM. The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.

YuGuang, Ye; Hong, Zou; Qiu-Gang, Zong; HongFei, Chen; JiQing, Zou; WeiHong, Shi; XiangQian, Yu; WeiYing, Zhong; YongFu, Wang; YiXin, Hao; ZhiYang, Liu; XiangHong, Jia; Bo, Wang; XiaoPing, Yang; XiaoYun, Hao;

Published by: Earth and Planetary Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.26464/epp2021021

Radiation belts; energetic electron detection; Pin-hole technology; Chinese navigation satellites; MEO; internal charging; Van Allen Probes

Energetic electron detection packages on board Chinese navigation satellites in MEO

Abstract Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E telescope technology, and a deep dielectric charging monitor (DDCM). The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30° field of view (FOV). The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30° cone-angle FOV. The ground test and calibration results indicate that these three sensors exhibit excellent performance. Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer (MagEIS) of the Van Allen Probes spacecraft, with an average relative deviation of 27.3\% for the energy spectra. The charging currents and voltages measured by the DDCM during storms are consistent with the high-energy electron observations of the HED, demonstrating the effectiveness of the DDCM. The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.

YuGuang, Ye; Hong, Zou; Qiu-Gang, Zong; HongFei, Chen; JiQing, Zou; WeiHong, Shi; XiangQian, Yu; WeiYing, Zhong; YongFu, Wang; YiXin, Hao; ZhiYang, Liu; XiangHong, Jia; Bo, Wang; XiaoPing, Yang; XiaoYun, Hao;

Published by: Earth and Planetary Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.26464/epp2021021

Radiation belts; energetic electron detection; Pin-hole technology; Chinese navigation satellites; MEO; internal charging; Van Allen Probes

Energetic electron detection packages on board Chinese navigation satellites in MEO

Abstract Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E telescope technology, and a deep dielectric charging monitor (DDCM). The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30° field of view (FOV). The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30° cone-angle FOV. The ground test and calibration results indicate that these three sensors exhibit excellent performance. Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer (MagEIS) of the Van Allen Probes spacecraft, with an average relative deviation of 27.3\% for the energy spectra. The charging currents and voltages measured by the DDCM during storms are consistent with the high-energy electron observations of the HED, demonstrating the effectiveness of the DDCM. The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.

YuGuang, Ye; Hong, Zou; Qiu-Gang, Zong; HongFei, Chen; JiQing, Zou; WeiHong, Shi; XiangQian, Yu; WeiYing, Zhong; YongFu, Wang; YiXin, Hao; ZhiYang, Liu; XiangHong, Jia; Bo, Wang; XiaoPing, Yang; XiaoYun, Hao;

Published by: Earth and Planetary Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.26464/epp2021021

Radiation belts; energetic electron detection; Pin-hole technology; Chinese navigation satellites; MEO; internal charging; Van Allen Probes

Energetic electron detection packages on board Chinese navigation satellites in MEO

Abstract Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E telescope technology, and a deep dielectric charging monitor (DDCM). The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30° field of view (FOV). The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30° cone-angle FOV. The ground test and calibration results indicate that these three sensors exhibit excellent performance. Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer (MagEIS) of the Van Allen Probes spacecraft, with an average relative deviation of 27.3\% for the energy spectra. The charging currents and voltages measured by the DDCM during storms are consistent with the high-energy electron observations of the HED, demonstrating the effectiveness of the DDCM. The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.

YuGuang, Ye; Hong, Zou; Qiu-Gang, Zong; HongFei, Chen; JiQing, Zou; WeiHong, Shi; XiangQian, Yu; WeiYing, Zhong; YongFu, Wang; YiXin, Hao; ZhiYang, Liu; XiangHong, Jia; Bo, Wang; XiaoPing, Yang; XiaoYun, Hao;

Published by: Earth and Planetary Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.26464/epp2021021

Radiation belts; energetic electron detection; Pin-hole technology; Chinese navigation satellites; MEO; internal charging; Van Allen Probes

Energetic electron detection packages on board Chinese navigation satellites in MEO

Abstract Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E telescope technology, and a deep dielectric charging monitor (DDCM). The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30° field of view (FOV). The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30° cone-angle FOV. The ground test and calibration results indicate that these three sensors exhibit excellent performance. Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer (MagEIS) of the Van Allen Probes spacecraft, with an average relative deviation of 27.3\% for the energy spectra. The charging currents and voltages measured by the DDCM during storms are consistent with the high-energy electron observations of the HED, demonstrating the effectiveness of the DDCM. The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.

YuGuang, Ye; Hong, Zou; Qiu-Gang, Zong; HongFei, Chen; JiQing, Zou; WeiHong, Shi; XiangQian, Yu; WeiYing, Zhong; YongFu, Wang; YiXin, Hao; ZhiYang, Liu; XiangHong, Jia; Bo, Wang; XiaoPing, Yang; XiaoYun, Hao;

Published by: Earth and Planetary Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.26464/epp2021021

Radiation belts; energetic electron detection; Pin-hole technology; Chinese navigation satellites; MEO; internal charging; Van Allen Probes

Energetic electron detection packages on board Chinese navigation satellites in MEO

Abstract Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E telescope technology, and a deep dielectric charging monitor (DDCM). The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30° field of view (FOV). The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30° cone-angle FOV. The ground test and calibration results indicate that these three sensors exhibit excellent performance. Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer (MagEIS) of the Van Allen Probes spacecraft, with an average relative deviation of 27.3\% for the energy spectra. The charging currents and voltages measured by the DDCM during storms are consistent with the high-energy electron observations of the HED, demonstrating the effectiveness of the DDCM. The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.

YuGuang, Ye; Hong, Zou; Qiu-Gang, Zong; HongFei, Chen; JiQing, Zou; WeiHong, Shi; XiangQian, Yu; WeiYing, Zhong; YongFu, Wang; YiXin, Hao; ZhiYang, Liu; XiangHong, Jia; Bo, Wang; XiaoPing, Yang; XiaoYun, Hao;

Published by: Earth and Planetary Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.26464/epp2021021

Radiation belts; energetic electron detection; Pin-hole technology; Chinese navigation satellites; MEO; internal charging; Van Allen Probes

Empirical loss timescales of slot region electrons due to plasmaspheric hiss based on Van Allen Probes observations

Abstract Based on Van Allen Probes observations, in this study we perform a statistical analysis of the spectral intensities of plasmaspheric hiss at L-shells of 1.8 – 3.0 in the slot region. Our results show that slot region hiss power intensifies with a strong day-night asymmetry as the level of substorm activity or L-shell increases. Using the statistical spectral profiles of plasmaspheric hiss, we calculate the drift- and bounce-averaged electron pitch angle diffusion coefficients and subsequently obtain the resultant electron loss timescales through 1-D Fokker-Planck simulations. We find that slot region electron loss timescales vary significantly from <1 day to several years, showing a strong dependence on electron energy, L-shell and substorm activity. We also construct an empirical model of slot region electron loss timescales due to scattering by plasmaspheric hiss, which agrees well with the 1-D simulation results and can be readily used in modeling the dynamics of slot region electrons. This article is protected by copyright. All rights reserved.

Zhu, Qi; Cao, Xing; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Fu, Song; Summers, Danny; Hua, Man; Lou, Yuequn; Ma, Xin; Guo, YingJie; Guo, DeYu; Zhang, Wenxun;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029057

Plasmaspheric Hiss; Slot region; Electron loss timescales; Van Allen Probes

Empirical loss timescales of slot region electrons due to plasmaspheric hiss based on Van Allen Probes observations

Abstract Based on Van Allen Probes observations, in this study we perform a statistical analysis of the spectral intensities of plasmaspheric hiss at L-shells of 1.8 – 3.0 in the slot region. Our results show that slot region hiss power intensifies with a strong day-night asymmetry as the level of substorm activity or L-shell increases. Using the statistical spectral profiles of plasmaspheric hiss, we calculate the drift- and bounce-averaged electron pitch angle diffusion coefficients and subsequently obtain the resultant electron loss timescales through 1-D Fokker-Planck simulations. We find that slot region electron loss timescales vary significantly from <1 day to several years, showing a strong dependence on electron energy, L-shell and substorm activity. We also construct an empirical model of slot region electron loss timescales due to scattering by plasmaspheric hiss, which agrees well with the 1-D simulation results and can be readily used in modeling the dynamics of slot region electrons. This article is protected by copyright. All rights reserved.

Zhu, Qi; Cao, Xing; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Fu, Song; Summers, Danny; Hua, Man; Lou, Yuequn; Ma, Xin; Guo, YingJie; Guo, DeYu; Zhang, Wenxun;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029057

Plasmaspheric Hiss; Slot region; Electron loss timescales; Van Allen Probes

Empirical loss timescales of slot region electrons due to plasmaspheric hiss based on Van Allen Probes observations

Abstract Based on Van Allen Probes observations, in this study we perform a statistical analysis of the spectral intensities of plasmaspheric hiss at L-shells of 1.8 – 3.0 in the slot region. Our results show that slot region hiss power intensifies with a strong day-night asymmetry as the level of substorm activity or L-shell increases. Using the statistical spectral profiles of plasmaspheric hiss, we calculate the drift- and bounce-averaged electron pitch angle diffusion coefficients and subsequently obtain the resultant electron loss timescales through 1-D Fokker-Planck simulations. We find that slot region electron loss timescales vary significantly from <1 day to several years, showing a strong dependence on electron energy, L-shell and substorm activity. We also construct an empirical model of slot region electron loss timescales due to scattering by plasmaspheric hiss, which agrees well with the 1-D simulation results and can be readily used in modeling the dynamics of slot region electrons. This article is protected by copyright. All rights reserved.

Zhu, Qi; Cao, Xing; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Fu, Song; Summers, Danny; Hua, Man; Lou, Yuequn; Ma, Xin; Guo, YingJie; Guo, DeYu; Zhang, Wenxun;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029057

Plasmaspheric Hiss; Slot region; Electron loss timescales; Van Allen Probes

Empirical loss timescales of slot region electrons due to plasmaspheric hiss based on Van Allen Probes observations

Abstract Based on Van Allen Probes observations, in this study we perform a statistical analysis of the spectral intensities of plasmaspheric hiss at L-shells of 1.8 – 3.0 in the slot region. Our results show that slot region hiss power intensifies with a strong day-night asymmetry as the level of substorm activity or L-shell increases. Using the statistical spectral profiles of plasmaspheric hiss, we calculate the drift- and bounce-averaged electron pitch angle diffusion coefficients and subsequently obtain the resultant electron loss timescales through 1-D Fokker-Planck simulations. We find that slot region electron loss timescales vary significantly from <1 day to several years, showing a strong dependence on electron energy, L-shell and substorm activity. We also construct an empirical model of slot region electron loss timescales due to scattering by plasmaspheric hiss, which agrees well with the 1-D simulation results and can be readily used in modeling the dynamics of slot region electrons. This article is protected by copyright. All rights reserved.

Zhu, Qi; Cao, Xing; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Fu, Song; Summers, Danny; Hua, Man; Lou, Yuequn; Ma, Xin; Guo, YingJie; Guo, DeYu; Zhang, Wenxun;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029057

Plasmaspheric Hiss; Slot region; Electron loss timescales; Van Allen Probes

Empirical loss timescales of slot region electrons due to plasmaspheric hiss based on Van Allen Probes observations

Abstract Based on Van Allen Probes observations, in this study we perform a statistical analysis of the spectral intensities of plasmaspheric hiss at L-shells of 1.8 – 3.0 in the slot region. Our results show that slot region hiss power intensifies with a strong day-night asymmetry as the level of substorm activity or L-shell increases. Using the statistical spectral profiles of plasmaspheric hiss, we calculate the drift- and bounce-averaged electron pitch angle diffusion coefficients and subsequently obtain the resultant electron loss timescales through 1-D Fokker-Planck simulations. We find that slot region electron loss timescales vary significantly from <1 day to several years, showing a strong dependence on electron energy, L-shell and substorm activity. We also construct an empirical model of slot region electron loss timescales due to scattering by plasmaspheric hiss, which agrees well with the 1-D simulation results and can be readily used in modeling the dynamics of slot region electrons. This article is protected by copyright. All rights reserved.

Zhu, Qi; Cao, Xing; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Fu, Song; Summers, Danny; Hua, Man; Lou, Yuequn; Ma, Xin; Guo, YingJie; Guo, DeYu; Zhang, Wenxun;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029057

Plasmaspheric Hiss; Slot region; Electron loss timescales; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data

Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Van Allen Probes (VAP) Mission versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase satellite is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board VAP (2012-2019) and Arase (2017-) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.;

Published by: Space Weather      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020SW002692

Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes

Evidence of Alfvenic Poynting flux as the primary driver of auroral motion during a geomagnetic substorm

Abstract Geomagnetic substorms are major energy transfer events where energy stored in the Earths magnetotail is released into the ionosphere. Substorm phenomena, including auroral activities, earthward Poynting flux, magnetic field dipolarization, etc, have been extensively studied. However, the complex interplay among them is not fully understood. In a fortuitous event on June 07, 2013, the twin Van Allen Probes (separated by 0.4 hour in local time) observed bursts of earthward Alfvenic Poynting flux in the vicinity of the plasma sheet boundary layer (PSBL). The Poynting flux bursts correlate with enhancements of auroral brightness around the footpoints of both spacecraft. This indicates a temporal and spatial correlation between the auroral brightening and Poynting flux bursts, and that the auroral motion is directly linked to the perpendicular expansion of the Alfven wave. These observations suggest that the Alfvenic Poynting flux is a primary driver for the auroral electron acceleration. Around the time of auroral brightening, a dipolarization was seen to propagate more than 4 hours in local time during a 20 min period. The azimuthal phase speed of this dipolarization (2 deg/min) is too small to explain the azimuthal motion of the aurora (13.6 deg/min), but the dipolarization could be related to the generation of the Alfvenic Poynting flux through phase mixing at strong density gradients like those in the PSBL. This article is protected by copyright. All rights reserved.

Tian, S.; Colpitts, C.; Wygant, J.; Cattell, C.; Ferradas, C.; Igl, A.; Larsen, B.; Reeves, G.; Donovan, E.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029019

Poynting flux; auroral physics; discrete arc; Dipolarization; Alfven waves; Van Allen Probes

Evidence of Alfvenic Poynting flux as the primary driver of auroral motion during a geomagnetic substorm

Abstract Geomagnetic substorms are major energy transfer events where energy stored in the Earths magnetotail is released into the ionosphere. Substorm phenomena, including auroral activities, earthward Poynting flux, magnetic field dipolarization, etc, have been extensively studied. However, the complex interplay among them is not fully understood. In a fortuitous event on June 07, 2013, the twin Van Allen Probes (separated by 0.4 hour in local time) observed bursts of earthward Alfvenic Poynting flux in the vicinity of the plasma sheet boundary layer (PSBL). The Poynting flux bursts correlate with enhancements of auroral brightness around the footpoints of both spacecraft. This indicates a temporal and spatial correlation between the auroral brightening and Poynting flux bursts, and that the auroral motion is directly linked to the perpendicular expansion of the Alfven wave. These observations suggest that the Alfvenic Poynting flux is a primary driver for the auroral electron acceleration. Around the time of auroral brightening, a dipolarization was seen to propagate more than 4 hours in local time during a 20 min period. The azimuthal phase speed of this dipolarization (2 deg/min) is too small to explain the azimuthal motion of the aurora (13.6 deg/min), but the dipolarization could be related to the generation of the Alfvenic Poynting flux through phase mixing at strong density gradients like those in the PSBL. This article is protected by copyright. All rights reserved.

Tian, S.; Colpitts, C.; Wygant, J.; Cattell, C.; Ferradas, C.; Igl, A.; Larsen, B.; Reeves, G.; Donovan, E.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029019

Poynting flux; auroral physics; discrete arc; Dipolarization; Alfven waves; Van Allen Probes

Evidence of Alfvenic Poynting flux as the primary driver of auroral motion during a geomagnetic substorm

Abstract Geomagnetic substorms are major energy transfer events where energy stored in the Earths magnetotail is released into the ionosphere. Substorm phenomena, including auroral activities, earthward Poynting flux, magnetic field dipolarization, etc, have been extensively studied. However, the complex interplay among them is not fully understood. In a fortuitous event on June 07, 2013, the twin Van Allen Probes (separated by 0.4 hour in local time) observed bursts of earthward Alfvenic Poynting flux in the vicinity of the plasma sheet boundary layer (PSBL). The Poynting flux bursts correlate with enhancements of auroral brightness around the footpoints of both spacecraft. This indicates a temporal and spatial correlation between the auroral brightening and Poynting flux bursts, and that the auroral motion is directly linked to the perpendicular expansion of the Alfven wave. These observations suggest that the Alfvenic Poynting flux is a primary driver for the auroral electron acceleration. Around the time of auroral brightening, a dipolarization was seen to propagate more than 4 hours in local time during a 20 min period. The azimuthal phase speed of this dipolarization (2 deg/min) is too small to explain the azimuthal motion of the aurora (13.6 deg/min), but the dipolarization could be related to the generation of the Alfvenic Poynting flux through phase mixing at strong density gradients like those in the PSBL. This article is protected by copyright. All rights reserved.

Tian, S.; Colpitts, C.; Wygant, J.; Cattell, C.; Ferradas, C.; Igl, A.; Larsen, B.; Reeves, G.; Donovan, E.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029019

Poynting flux; auroral physics; discrete arc; Dipolarization; Alfven waves; Van Allen Probes

Evidence of Alfvenic Poynting flux as the primary driver of auroral motion during a geomagnetic substorm

Abstract Geomagnetic substorms are major energy transfer events where energy stored in the Earths magnetotail is released into the ionosphere. Substorm phenomena, including auroral activities, earthward Poynting flux, magnetic field dipolarization, etc, have been extensively studied. However, the complex interplay among them is not fully understood. In a fortuitous event on June 07, 2013, the twin Van Allen Probes (separated by 0.4 hour in local time) observed bursts of earthward Alfvenic Poynting flux in the vicinity of the plasma sheet boundary layer (PSBL). The Poynting flux bursts correlate with enhancements of auroral brightness around the footpoints of both spacecraft. This indicates a temporal and spatial correlation between the auroral brightening and Poynting flux bursts, and that the auroral motion is directly linked to the perpendicular expansion of the Alfven wave. These observations suggest that the Alfvenic Poynting flux is a primary driver for the auroral electron acceleration. Around the time of auroral brightening, a dipolarization was seen to propagate more than 4 hours in local time during a 20 min period. The azimuthal phase speed of this dipolarization (2 deg/min) is too small to explain the azimuthal motion of the aurora (13.6 deg/min), but the dipolarization could be related to the generation of the Alfvenic Poynting flux through phase mixing at strong density gradients like those in the PSBL. This article is protected by copyright. All rights reserved.

Tian, S.; Colpitts, C.; Wygant, J.; Cattell, C.; Ferradas, C.; Igl, A.; Larsen, B.; Reeves, G.; Donovan, E.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029019

Poynting flux; auroral physics; discrete arc; Dipolarization; Alfven waves; Van Allen Probes

Evidence of Alfvenic Poynting flux as the primary driver of auroral motion during a geomagnetic substorm

Abstract Geomagnetic substorms are major energy transfer events where energy stored in the Earths magnetotail is released into the ionosphere. Substorm phenomena, including auroral activities, earthward Poynting flux, magnetic field dipolarization, etc, have been extensively studied. However, the complex interplay among them is not fully understood. In a fortuitous event on June 07, 2013, the twin Van Allen Probes (separated by 0.4 hour in local time) observed bursts of earthward Alfvenic Poynting flux in the vicinity of the plasma sheet boundary layer (PSBL). The Poynting flux bursts correlate with enhancements of auroral brightness around the footpoints of both spacecraft. This indicates a temporal and spatial correlation between the auroral brightening and Poynting flux bursts, and that the auroral motion is directly linked to the perpendicular expansion of the Alfven wave. These observations suggest that the Alfvenic Poynting flux is a primary driver for the auroral electron acceleration. Around the time of auroral brightening, a dipolarization was seen to propagate more than 4 hours in local time during a 20 min period. The azimuthal phase speed of this dipolarization (2 deg/min) is too small to explain the azimuthal motion of the aurora (13.6 deg/min), but the dipolarization could be related to the generation of the Alfvenic Poynting flux through phase mixing at strong density gradients like those in the PSBL. This article is protected by copyright. All rights reserved.

Tian, S.; Colpitts, C.; Wygant, J.; Cattell, C.; Ferradas, C.; Igl, A.; Larsen, B.; Reeves, G.; Donovan, E.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029019

Poynting flux; auroral physics; discrete arc; Dipolarization; Alfven waves; Van Allen Probes

Evidence of Alfvenic Poynting flux as the primary driver of auroral motion during a geomagnetic substorm

Abstract Geomagnetic substorms are major energy transfer events where energy stored in the Earths magnetotail is released into the ionosphere. Substorm phenomena, including auroral activities, earthward Poynting flux, magnetic field dipolarization, etc, have been extensively studied. However, the complex interplay among them is not fully understood. In a fortuitous event on June 07, 2013, the twin Van Allen Probes (separated by 0.4 hour in local time) observed bursts of earthward Alfvenic Poynting flux in the vicinity of the plasma sheet boundary layer (PSBL). The Poynting flux bursts correlate with enhancements of auroral brightness around the footpoints of both spacecraft. This indicates a temporal and spatial correlation between the auroral brightening and Poynting flux bursts, and that the auroral motion is directly linked to the perpendicular expansion of the Alfven wave. These observations suggest that the Alfvenic Poynting flux is a primary driver for the auroral electron acceleration. Around the time of auroral brightening, a dipolarization was seen to propagate more than 4 hours in local time during a 20 min period. The azimuthal phase speed of this dipolarization (2 deg/min) is too small to explain the azimuthal motion of the aurora (13.6 deg/min), but the dipolarization could be related to the generation of the Alfvenic Poynting flux through phase mixing at strong density gradients like those in the PSBL. This article is protected by copyright. All rights reserved.

Tian, S.; Colpitts, C.; Wygant, J.; Cattell, C.; Ferradas, C.; Igl, A.; Larsen, B.; Reeves, G.; Donovan, E.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029019

Poynting flux; auroral physics; discrete arc; Dipolarization; Alfven waves; Van Allen Probes

Upper limit of proton anisotropy and its relation to EMIC waves in the inner magnetosphere

Abstract Proton anisotropy in velocity space has been generally accepted as a major parameter for exciting electromagnetic ion cyclotron (EMIC) waves. In this study, we estimate the proton anisotropy parameter as defined by the linear resonance theory using data from the Van Allen Probes mission. Our investigation uses the measurements of the inner magnetosphere (L < 6) from January 2013 to February 2018. We find that the proton anisotropy is always clearly limited by an upper bound and it well follows an inverse relationship with the parallel proton β (the ratio of the plasma pressure to the magnetic pressure) within a certain range. This upper bound exists over wide spatial regions, AE conditions, and resonance energies regardless of the presence of EMIC waves. EMIC waves occur when the anisotropy lies below but close to this upper bound within a narrow plasma β range: The lower cutoff β is due to an excessively high anisotropy threshold and the upper cutoff β is possibly due to the predominant role of a faster-growing mirror mode instability. We also find that the anisotropy during the observed EMIC waves is unstable, leading to the linear ion cyclotron instability. This result implies that the upper bound of the anisotropy is due to nonlinear processes. This article is protected by copyright. All rights reserved.

Noh, Sung-Jun; Lee, Dae-Young; Kim, Hyomin; Lanzerotti, Louis; Gerrard, Andrew; Skoug, Ruth;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028614

Proton Anisotropy; Ion cyclotron instability; Proton distribution; Van Allen Probes; Wave-particle interaction

Upper limit of proton anisotropy and its relation to EMIC waves in the inner magnetosphere

Abstract Proton anisotropy in velocity space has been generally accepted as a major parameter for exciting electromagnetic ion cyclotron (EMIC) waves. In this study, we estimate the proton anisotropy parameter as defined by the linear resonance theory using data from the Van Allen Probes mission. Our investigation uses the measurements of the inner magnetosphere (L < 6) from January 2013 to February 2018. We find that the proton anisotropy is always clearly limited by an upper bound and it well follows an inverse relationship with the parallel proton β (the ratio of the plasma pressure to the magnetic pressure) within a certain range. This upper bound exists over wide spatial regions, AE conditions, and resonance energies regardless of the presence of EMIC waves. EMIC waves occur when the anisotropy lies below but close to this upper bound within a narrow plasma β range: The lower cutoff β is due to an excessively high anisotropy threshold and the upper cutoff β is possibly due to the predominant role of a faster-growing mirror mode instability. We also find that the anisotropy during the observed EMIC waves is unstable, leading to the linear ion cyclotron instability. This result implies that the upper bound of the anisotropy is due to nonlinear processes. This article is protected by copyright. All rights reserved.

Noh, Sung-Jun; Lee, Dae-Young; Kim, Hyomin; Lanzerotti, Louis; Gerrard, Andrew; Skoug, Ruth;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028614

Proton Anisotropy; Ion cyclotron instability; Proton distribution; Van Allen Probes; Wave-particle interaction

Dependence of Relativistic Electron Precipitation in the Ionosphere on EMIC Wave Minimum Resonant Energy at the Conjugate Equator

Abstract We investigate relativistic electron precipitation events detected by POES in low-Earth orbit in close conjunction with Van Allen Probe A observations of EMIC waves near the geomagnetic equator. We show that the occurrence rate of > 0.7 MeV electron precipitation recorded by POES during those times strongly increases, reaching statistically significant levels when the minimum electron energy for cyclotron resonance with hydrogen or helium band EMIC waves at the equator decreases below ≃ 1.0 − 2.5 MeV, as expected from quasi-linear theory. Both hydrogen and helium band EMIC waves can be effective in precipitating MeV electrons. However, > 0.7 MeV electron precipitation is more often observed (at statistically significant levels) when the minimum electron energy for cyclotron resonance with hydrogen band waves is low (Emin = 0.6 − 1.0 MeV), whereas it is more often observed when the minimum electron energy for cyclotron resonance with helium band waves is slightly larger (Emin = 1.0 − 2.5 MeV), indicative of warm plasma effects for waves approaching the He+ gyrofrequency. We further show that most precipitation events had energies > 0.7 − 1.0 MeV, consistent with the estimated minimum energy (Emin ∼ 0.6 − 2.5 MeV) of cyclotron resonance with the observed EMIC waves during the majority of these events. However, 4 out of the 12 detected precipitation events cannot be explained by electron quasi-linear scattering by the observed EMIC waves, and 12 out of 20 theoretically expected precipitation events were not detected by POES, suggesting the possibility of nonlinear effects likely present near the magnetic equator, or warm plasma effects, and/or narrowly localized bursts of EMIC waves. This article is protected by copyright. All rights reserved.

Zhang, X.-J.; Mourenas, D.; Shen, X.-C.; Qin, M.; Artemyev, A.; Ma, Q.; Li, W.; Hudson, M.; Angelopoulos, V.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 04/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2021JA029193

EMIC waves; relativistic electron precipitation; minimum resonant energy; Van Allen Probes; POES; Radiation belts