行星际激波导致的磁尾等离子片中ULF波动事件

ULF Wave in the Magnetotail Plasma Sheet Induced by Interplanetary Shock

磁层中的超低频(ULF)波动在太阳凤和磁层之间的能量输运过程中具有重要作用.ULF波动主要发生在内磁层,且内磁层中ULF波动影响粒子的加速及沉降,而在夜侧磁层尤其是磁尾等离子片中观测到的ULF波动比较少.基于中国自主磁层探测卫星TC-1的观测数据,发现了两例行星际激波导致的磁尾中心等离子片中ULF波动事件,并发现这两例ULF事例都包含很强的环向模驻波分量,与以往THEMIS卫星报道的同类事件观测特征相符.根据ULF波的观测特征,分析了这两例ULF波动的可能触发机制.研究结果有助于深入理解磁层对行星际激波的全球响应.

Ultra Low Frequency(ULF)waves play an important role in energy transport from the solar wind into the magnetosphere.The ULF waves have often been observed in the dayside magnetosphere,which affects the acceleration and deceleration of energetic particles in inner magnetosphere,and is also responsible for the particle precipitation.There have been few reports of ULF wave activity on the nightside.Here based on the observations of TC-1 in the magnetotail central plasma sheet,two ULF wave events induced by two interplanetary shocks are identified and analyzed.East-west magnetic and radial electric field perturbations,which denote the toroidal mode,are found to be stronger for the two cases and their phase difference are nearly 90°.These features are consistent with previous observations from THEMIS.Several possible mechanisms for these kinds of ULF wave excitation are discussed according to the observational characteristics.It helps to deepen the understanding of the global response of the magnetosphere to interplanetary shocks.