Excitation and Dispersion of Whistler Waves Inside the Contracting Magnetic Hole

IF 2.6 2区地球科学 Q2 ASTRONOMY & ASTROPHYSICS Journal of Geophysical Research: Space Physics Pub Date : 2025-01-22 DOI:10.1029/2024JA033524

Z. Y. Xu, Z. Wang, H. S. Fu, W. D. Fu, W. Z. Zhang, Y. Yu, Z. Z. Guo, J. B. Cao

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Abstract

Magnetic holes (MHs) are the magnetic structures characterized by the significant decreases of magnitude field, and they have been widely observed in various space plasmas. The high-resolution observations by NASA's Magnetospheric Multiscale Mission and the Dispersion RelAtion From Timing (DRAFT) method enable us to study the wave-particle interactions in MHs in great detail. In this paper, we report whistler waves in a contracting MH and reveal their dispersion relation with DRAFT method, which is well-consistent with the theoretical prediction. During the excitation of the whistler waves, we also find the formation of pancake distribution (corresponding to electron temperature anisotropy T_⊥/T_// > 1). By calculating the growth rate of the whistler waves with an analytical model, we find such waves are generated by the temperature anisotropy (T_⊥/T_// > 1) at the center of MH, which is formed during the contraction. These results suggest that wave-particle interactions may be closely related to the large-scale evolution of the MH structures.

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