Quantitative Evaluation of Radial Diffusion and Local Acceleration Processes During GEM Challenge Events

Q Ma; W Li; C. A Kletzing; W. S Kurth; J Bortnik; G. B Hospodarsky; R. M Thorne; X Chu; L. G Ozeke; G. D Reeves; M. J Engebretson; H. E Spence; D. N Baker; J. B Blake; J. F Fennell; S. G Claudepierre

doi:10.1002/2017JA025114

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Quantitative Evaluation of Radial Diffusion and Local Acceleration Processes During GEM Challenge Events

Journal article

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Quantitative Evaluation of Radial Diffusion and Local Acceleration Processes During GEM Challenge Events

Q Ma, W Li, C. A Kletzing, W. S Kurth, J Bortnik, G. B Hospodarsky, R. M Thorne, X Chu, L. G Ozeke, G. D Reeves, …

Journal of geophysical research. Space physics, Vol.123(3), pp.1938-1952

03/2018

DOI: 10.1002/2017JA025114

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Abstract

We simulate the radiation belt electron flux enhancements during selected Geospace Environment Modeling (GEM) challenge events to quantitatively compare the major processes involved in relativistic electron acceleration under different conditions. Van Allen Probes observed significant electron flux enhancement during both the storm time of 17–18 March 2013 and non–storm time of 19–20 September 2013, but the distributions of plasma waves and energetic electrons for the two events were dramatically different. During 17–18 March 2013, the SYM‐H minimum reached −130 nT, intense chorus waves (peak Bw ~140 pT) occurred at 3.5 < L < 5.5, and several hundred keV to several MeV electron fluxes increased by ~2 orders of magnitude mostly at 3.5 < L < 5.5. During 19–20 September 2013, the SYM‐H remained higher than −30 nT, modestly intense chorus waves (peak Bw ~80 pT) occurred at L > 5.5, and electron fluxes at energies up to 3 MeV increased by a factor of ~5 at L > 5.5. The two electron flux enhancement events were simulated using the available wave distribution and diffusion coefficients from the GEM focus group Quantitative Assessment of Radiation Belt Modeling. By comparing the individual roles of local electron heating and radial transport, our simulation indicates that resonant interaction with chorus waves is the dominant process that accounts for the electron flux enhancement during the storm time event particularly near the flux peak locations, while radial diffusion by ultralow‐frequency waves plays a dominant role in the enhancement during the non–storm time event. Incorporation of both processes reasonably reproduces the observed location and magnitude of electron flux enhancement. Key Points Energetic electron fluxes are enhanced during storm and non–storm time events, but wave and electron structures are dramatically different Local heating by whistler mode chorus wave is the major contributor to the flux enhancement near the peak during 17–18 March 2013 Radial diffusion by ultralow‐frequency wave is the major contributor to the observed flux enhancement during 19–20 September 2013

electron acceleration

radial diffusion

radiation belt simulation

Van Allen Probes observation

whistler mode waves

Details

Title: Subtitle: Quantitative Evaluation of Radial Diffusion and Local Acceleration Processes During GEM Challenge Events
Creators: Q Ma - Boston University
W Li - Boston University
C. A Kletzing - University of Iowa
W. S Kurth - University of Iowa
J Bortnik - University of California, Los Angeles
G. B Hospodarsky - University of Iowa
R. M Thorne - University of California, Los Angeles
X Chu - University of California, Los Angeles
L. G Ozeke - University of Alberta
G. D Reeves - Los Alamos National Laboratory
M. J Engebretson - Augsburg University
H. E Spence - University of New Hampshire
D. N Baker - University of Colorado Boulder
J. B Blake - The Aerospace Corporation
J. F Fennell - The Aerospace Corporation
S. G Claudepierre - The Aerospace Corporation
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.123(3), pp.1938-1952
DOI: 10.1002/2017JA025114
ISSN: 2169-9380
eISSN: 2169-9402
Number of pages: 15
Grant note: NASA (NAS5‐01072; NNX15AI96G; NNX11AR64G; NNX14AN85G; NNX14AI18G; NNX17AD15G; NNX17AG07G) National Science Foundation (AGS 1451911; AGS‐1723588; PLR‐1341493; AGS‐1651263) AFOSR (FA9550‐15‐1‐0158) JHU/APL (967399; 921647)
Language: English
Date published: 03/2018
Academic Unit: Physics and Astronomy
Record Identifier: 9984199771502771

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