Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities

Yihua He; D. N Baker; C. A Kletzing; Fuliang Xiao; W. S Kurth; Qinghua Zhou; G. B Hospodarsky; Chang Yang; Si Liu; H. E Spence; G. D Reeves; H. O Funsten; J. B Blake

doi:10.1002/2015JA021376

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Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities

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Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities

Yihua He, D. N Baker, C. A Kletzing, Fuliang Xiao, W. S Kurth, Qinghua Zhou, G. B Hospodarsky, Chang Yang, Si Liu, H. E Spence, …

Journal of geophysical research. Space physics, Vol.120(8), pp.6371-6385

08/2015

DOI: 10.1002/2015JA021376

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Abstract

We report correlated data on nightside chorus waves and energetic electrons during two small storm periods: 1 November 2012 (Dst≈−45) and 14 January 2013 (Dst≈−18). The Van Allen Probes simultaneously observed strong chorus waves at locations L = 5.8–6.3, with a lower frequency band 0.1–0.5fce and a peak spectral density ∼10−4 nT2/Hz. In the same period, the fluxes and anisotropy of energetic (∼10–300 keV) electrons were greatly enhanced in the interval of large negative interplanetary magnetic field Bz. Using a bi-Maxwellian distribution to model the observed electron distribution, we perform ray tracing simulations to show that nightside chorus waves are indeed produced by the observed electron distribution with a peak growth for a field-aligned propagation approximately between 0.3fce and 0.4fce, at latitude <7°. Moreover, chorus waves launched with initial normal angles either θ<90° or >90° propagate along the field either northward or southward and then bounce back either away from Earth for a lower frequency or toward Earth for higher frequencies. The current results indicate that nightside chorus waves can be excited even during weak geomagnetic activities in cases of continuous injection associated with negative Bz. Moreover, we examine a dayside event during a small storm C on 8 May 2014 (Dst≈−45) and find that the observed anisotropic energetic electron distributions potentially contribute to the generation of dayside chorus waves, but this requires more thorough studies in the future.

chorus wave excitation

energetic electrons

geomagnetic storm

Van Allen probes results

wave-particle interaction

Details

Title: Subtitle: Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities
Creators: Yihua He - Changsha University of Science and Technology
D. N Baker - University of Colorado Boulder
C. A Kletzing - University of Iowa
Fuliang Xiao - Changsha University of Science and Technology
W. S Kurth - University of Iowa
Qinghua Zhou - Changsha University of Science and Technology
G. B Hospodarsky - University of Iowa
Chang Yang - Changsha University of Science and Technology
Si Liu - Changsha University of Science and Technology
H. E Spence - University of New Hampshire
G. D Reeves - Los Alamos National Laboratory
H. O Funsten - Los Alamos National Laboratory
J. B Blake - The Aerospace Corporation
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.120(8), pp.6371-6385
Publisher: Blackwell Publishing Ltd
DOI: 10.1002/2015JA021376
ISSN: 2169-9380
eISSN: 2169-9402
Number of pages: 15
Grant note: DOI: 10.13039/501100001809, name: National Natural Science Foundation of China, award: 41404130, 41274165, 41204114
Language: English
Date published: 08/2015
Academic Unit: Physics and Astronomy
Record Identifier: 9984199730102771

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