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Frequency‐Dependent Modulation of Whistler‐Mode Waves by Density Irregularities During the Recovery Phase of a Geomagnetic Storm
Author(s) -
Liu Xu,
Gu Wenyao,
Xia Zhiyang,
Chen Lunjin,
Horne Richard B.
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2021gl093095
Subject(s) - whistler , physics , plasmasphere , van allen radiation belt , computational physics , geophysics , earth's magnetic field , amplitude , ionosphere , magnetosphere , wave propagation , geomagnetic storm , crest , electron precipitation , optics , electron , plasma , magnetic field , quantum mechanics
Density irregularities near the plasmapause are commonly observed and play an important role in whistler‐mode wave excitation and propagation. In this study, we report a frequency‐dependent modulation event of whistler‐mode waves by background density irregularities during a geomagnetic storm. Higher‐frequency whistler waves (near 0.5f c e , wheref c eis the equatorial electron cyclotron frequency) are trapped in the density trough regions due to the small refractive index near the parallel direction, while lower‐frequency whistler waves (below 0.02f c e ) are trapped in the density crest regions due to the refractive index maximum along the parallel direction. In addition to the modulation, we also find that, quantitatively, the wave amplitude of the higher‐ (lower‐) frequency whistler‐mode waves is anti‐correlated (correlated) with the relative plasma density variation. Our study suggests the importance of density irregularity dynamics in controlling whistler‐mode wave intensity, and thus radiation belt dynamics.