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Excitation of nightside magnetosonic waves observed by Van Allen Probes
Author(s) -
Zhou Qinghua,
Xiao Fuliang,
Yang Chang,
Liu Si,
Kletzing C. A.,
Kurth W. S.,
Hospodarsky G. B.,
Spence H. E.,
Reeves G. D.,
Funsten H. O.,
Blake J. B.,
Baker D. N.,
Wygant J. R.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020481
Subject(s) - physics , van allen probes , ring current , proton , geomagnetic storm , excitation , earth's magnetic field , range (aeronautics) , instability , atomic physics , ray tracing (physics) , computational physics , magnetosphere , magnetic field , optics , van allen radiation belt , nuclear physics , plasma , mechanics , quantum mechanics , materials science , composite material
During the recovery phase of the geomagnetic storm on 30–31 March 2013, Van Allen Probe A detected enhanced magnetosonic (MS) waves in a broad range of L = 1.8–4.7 and magnetic local time (MLT) = 17–22 h, with a frequency range ∼10–100 Hz. In the meanwhile, distinct proton ring distributions with peaks at energies of ∼10 keV, were also observed in L = 3.2–4.6 and L = 5.0–5.6. Using a subtracted bi‐Maxwellian distribution to model the observed proton ring distribution, we perform three‐dimensional ray tracing to investigate the instability, propagation, and spatial distribution of MS waves. Numerical results show that nightside MS waves are produced by proton ring distribution and grow rapidly from the source location L = 5.6 to the location L = 5.0 but remain nearly stable at locations L < 5.0. Moreover, waves launched toward lower L shells with different initial azimuthal angles propagate across different MLT regions with divergent paths at first, then gradually turn back toward higher L shells and propagate across different MLT regions with convergent paths. The current results further reveal that MS waves are generated by a ring distribution of ∼10 keV proton and proton ring in one region can contribute to the MS wave power in another region.