Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 48, Issue 22, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2021GL096056
Keywords
magnetic hole; whistler-mode waves; wave-particle interaction; butterfly distribution
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Funding
- National Natural Science Foundation of China [41974195, 42130211]
- China Postdoctoral Science Foundation [2021M691395]
- Interdisciplinary Innovation Fund of Natural Science from the Nanchang University [9166-27060003-YB14]
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The study reveals the presence of quasi-periodic whistler-mode waves at the center of a macroscale magnetic hole near Earth's magnetopause, corresponding to electron temperature anisotropy. These waves are accompanied by a significant ultra-low frequency wave of the background magnetic field, exacerbating the evolution of the magnetic hole and contributing to the formation of electron pitch angle distribution.
We report the quasi-periodic whistler-mode waves corresponding to electron temperature anisotropy T-perpendicular to/T-// < 1 at the center of a macroscale magnetic hole (MH) near the Earth's magnetopause observed by the Magnetospheric Multiscale mission. A significant ultra-low frequency (ULF) wave of background magnetic field was observed in this MH. The ULF wave dramatically exacerbates the evolution of MH and the formation of the donut-shaped electron pitch angle distribution (PAD) in the macroscale MH. When the whistler-mode waves were generated, they are consistent with troughs of the ULF wave and density increases, which is also related to the butterfly type PAD at those moments. The analysis of dispersion relation and cyclotron resonance condition indicate that whistler-mode waves were mainly generated by the butterfly type PAD of electrons. Our results provides new insights into one possible excitation mechanism of whistler-mode wave.
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