地球磁尾磁通量绳中哨声波的统计研究  

Statistical study of whistler waves in magnetic flux ropes in the Earth's magnetotail

作　　者：宋广进 黄狮勇 姜奎 袁志刚[1] 魏云云 张健[1] 吴红红 王朝 徐思博 熊启洋 林仁桐 余琳 王长梦 Song Guangjin;Huang Shiyong;Jiang Kui;Yuan Zhigang;Wei Yunyun;Zhang Jian;Wu Honghong;Wang Zhao;Xu Sibo;Xiong Qiyang;Lin Rentong;Yu Lin;Wang Changmeng(Electronic Information School,Wuhan University,Wuhan 430072,China;Hubei University of Arts and Science,Xiangyang 431053,China)

机构地区：[1]武汉大学电子信息学院,武汉430072 [2]湖北文理学院,襄阳431053

出　　处：《地球与行星物理论评（中英文）》2024年第5期583-594,共12页Reviews of Geophysics and Planetary Physics

基　　金：国家自然科学基金资助项目(42074196,41925018);中国博士后创新人才支持计划(BX20220238)。

摘　　要：哨声波被认为与地球磁尾磁通量绳的动力学有着密切的联系.之前的关于磁通量绳中哨声波的研究都是基于少数几个事件开展分析,并没有给出不同运动方向磁通量绳中的不同频带哨声波的空间分布特征,以及磁场功率谱密度和激发机制等.本文基于磁层多尺度卫星在2017年5月至8月穿越磁尾期间的观测数据,对地球磁尾磁通量绳中的哨声波进行了统计研究.根据磁场变化特征,磁通量绳被分成三个部分:前边界区、核心区和后边界区.根据与当地电子回旋频率(f_(ce))的相对大小,哨声波被分为下带(0.1f_(ce)~0.5f_(ce))和上带(0.5f_(ce)~f_(ce))哨声波.本文分别研究了地球磁尾地向运动和尾向运动磁通量绳中的下带和上带哨声波的空间分布特征,以及磁场功率谱密度和激发机制等.本文研究发现:(1)地球磁尾磁通量绳中观测到的哨声波主要是下带哨声波;(2)下带和上带哨声波都更易在地向运动和尾向运动磁通量绳的后边界区被观测到,并且在该区域它们的磁场功率谱强度也高于其他区域;(3)地向运动磁通量绳核心区的中心区域的下带和上带哨声波和尾向运动磁通量绳核心区的中心区域的下带哨声波可能是由垂直电子温度各向异性激发的;(4)在排除掉具有垂直电子温度各向异性的哨声波后,地向运动和尾向运动磁通量绳后边界区的上带哨声波可能是由电子束激发.本文的研究结果有助于理解哨声波对地球磁尾磁通量绳演化的影响和哨声波在磁尾动力学中所起的作用.Whistler waves are believed to have close relationship with the dynamics of the magnetic flux ropes(FRs)in the Earth's magnetotail.Previous studies about whistler waves in FRs were mainly based on event analysis.However,several key issues should be investigated from a statistical perspective,such as the spatial distributions of whistler waves in FRs with different motion directions,the frequency ranges of whistler waves,as well as the magnetic field power spectral densities(PSDs)and the excitation mechanisms of whistler waves.In this study,using the unprecedented high-resolution data from the magnetospheric multiscale(MMS)mission during the periods of magnetotail crossing between May and August in 2017,we perform a detailed statistical study on the whistler waves in the Earth's magnetotail FRs.Based on the magnetic field variation characteristics,the FRs are divided into three regions:the leading draping region,the core region,and the trailing draping region.Moreover,whistler waves are categorized into two types:low-band whistler waves with a frequency range between 0.1f_(ce)(f_(ce) is the local electron cyclotron frequency)and 0.5f_(ce),and upper-band whistler waves with a frequency range from 0.5f_(ce) to f_(ce).We separately investigate the spatial distribution characteristics,the magnetic-field PSDs,and excitation mechanisms of low-band whistler waves and upper-band whistler waves in earthward and tailward FRs.Finally,our research findings can be summarized as follows:(1)Whistler waves in the Earth’s magnetotail FRs are primarily lower-band ones;(2)More whistler waves along with more intense magnetic-field PSDs in the two frequency ranges both tend to occur in the trailing draping region;(3)The electron temperature with a dominant perpendicular anisotropy can account for the generation of low-band and upper-band whistler waves in the center region of core region of earthward FRs and low-band whistler waves in the center region of core region of tailward FRs;(4)In addition,the electron beams may provide free

关 键 词：地球磁尾 磁通量绳 哨声波 

分 类 号：P354[天文地球—空间物理学]