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Whistler‐Mode Waves Trapped by Density Irregularities in the Earth's Magnetosphere
Author(s) -
Ke Yangguang,
Chen Lunjin,
Gao Xinliang,
Lu Quanming,
Wang Xueyi,
Chen Rui,
Chen Huayue,
Wang Shui
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 - 10.1029/2020gl092305
Subject(s) - whistler , physics , van allen radiation belt , magnetosphere , computational physics , plasmasphere , electromagnetic radiation , geophysics , amplitude , wave propagation , electron density , electron , magnetic field , optics , quantum mechanics
Whistler‐mode waves are electromagnetic waves pervasively observed in the Earth's and other planetary magnetospheres. They are considered to be mainly responsible for producing the hazardous radiation and diffuse aurora, which heavily relies on their properties. Density irregularities, frequently observed in the Earth's magnetospheres, are found to change largely the properties of whistler‐mode waves. Here we report, using Van Allen Probes measurements, whistler‐mode waves strongly modulated by two different density enhancements. With particle‐in‐cell simulations, we propose wave trapping caused by field‐aligned density irregularities (ducts) may account for this phenomenon. Simulation results show that whistler‐mode waves can be trapped inside the enhanced density ducts. These trapped waves remain quasi‐parallel and usually get much larger amplitudes than those unducted whistler waves during propagation away from the magnetic equator, and tend to focus at a spatially narrow channel, consistent with observations. Our results imply density irregularities may be significant to modulate radiation‐belt electrons.