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Gap Formation Around 0.5Ω e of Whistler‐Mode Waves Excited by Electron Temperature Anisotropy
Author(s) -
Chen Huayue,
Gao Xinliang,
Lu Quanming,
Sauer Konrad,
Chen Rui,
Yao Jiansheng,
Wang Shui
Publication year - 2021
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja028631
Subject(s) - whistler , physics , excited state , dispersion relation , electron , anisotropy , atomic physics , cyclotron resonance , computational physics , condensed matter physics , optics , cyclotron , quantum mechanics
With a one‐dimensional particle‐in‐cell simulation model, we have investigated the gap formation around 0.5 Ω eof the quasi‐parallel whistler‐mode waves excited by an electron temperature anisotropy. When the frequencies of excited waves in the linear stage cross 0.5 Ω e , or when they are slightly larger than 0.5 Ω ebut then drift to lower values, the Landau resonance can make the electron distribution form a beam‐like/plateau population. Such an electron distribution only slightly changes the dispersion relation of whistler‐mode waves, but can cause severe damping around 0.5 Ω evia cyclotron resonance. At last, the wave spectrum is separated into two bands with a power gap around 0.5 Ω e . The condition under different electron temperature anisotropy and plasma beta is also surveyed for such kind of power gap. Besides, when only the waves with frequencies lower than 0.5 Ω eare excited in the linear stage, a power gap can also be formed due to the wave‐wave interactions, i.e., lower band cascade. Our study provides a clue to reveal the well‐known 0.5 Ω epower gap of whistler‐mode waves ubiquitously observed in the inner magnetosphere.