Kitamura N, Amano T, Omura Y, Boardsen S A, Gershman D J, Miyoshi Y, Kitahara M, Katoh Y, Kojima H, Nakamura S, Shoji M, Saito Y, Yokota S, Giles B L, Paterson W R, Pollock C J, Barrie A C, Skeberdis D G, Kreisler S, Le Contel O, Russell C T, Strangeway R J, Lindqvist P-A, Ergun R E, Torbert R B, Burch J L
Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan.
Department of Earth and Planetary Science, Graduate School of Science, the University of Tokyo, Tokyo, Japan.
Nat Commun. 2022 Oct 28;13(1):6259. doi: 10.1038/s41467-022-33604-2.
Electromagnetic whistler-mode waves in space plasmas play critical roles in collisionless energy transfer between the electrons and the electromagnetic field. Although resonant interactions have been considered as the likely generation process of the waves, observational identification has been extremely difficult due to the short time scale of resonant electron dynamics. Here we show strong nongyrotropy, which rotate with the wave, of cyclotron resonant electrons as direct evidence for the locally ongoing secular energy transfer from the resonant electrons to the whistler-mode waves using ultra-high temporal resolution data obtained by NASA's Magnetospheric Multiscale (MMS) mission in the magnetosheath. The nongyrotropic electrons carry a resonant current, which is the energy source of the wave as predicted by the nonlinear wave growth theory. This result proves the nonlinear wave growth theory, and furthermore demonstrates that the degree of nongyrotropy, which cannot be predicted even by that nonlinear theory, can be studied by observations.
空间等离子体中的电磁哨声波在电子与电磁场之间的无碰撞能量转移中起着关键作用。尽管共振相互作用被认为是这些波可能的产生过程，但由于共振电子动力学的时间尺度很短，观测识别一直极为困难。在这里，我们利用美国国家航空航天局（NASA）磁层多尺度（MMS）任务在磁鞘中获得的超高时间分辨率数据，展示了与波一起旋转的回旋共振电子的强烈非旋性，作为从共振电子到哨声波的局部持续长期能量转移的直接证据。非旋性电子携带共振电流，这是非线性波增长理论预测的波的能量来源。这一结果证明了非线性波增长理论，此外还表明，即使是非线性理论也无法预测的非旋性程度，可以通过观测来研究。
