磁暴期间电离层电磁离子回旋波的地方时分布差异  

Local Time Differences in the Ionospheric Electromagnetic Ion Cyclotron Waves during Storm Time

作　　者：孙璐媛 王慧[1] 何杨帆 SUN Luyuan;WANG Hui;HE Yangfan(Department of Space Physics,School of Electronic Information,Wuhan University,Wuhan 430072)

机构地区：[1]武汉大学电子信息学院空间物理系,武汉430072

出　　处：《空间科学学报》2021年第2期250-260,共11页Chinese Journal of Space Science

基　　金：国家自然科学基金项目资助(41974182,41431073)。

摘　　要：利用Swarm卫星的高精度(50 Hz)磁场观测数据,对2015年3月16—25日磁暴期间中纬度电离层电磁离子回旋(EMIC)波时空分布特征进行了研究.结果表明:晨侧EMIC波事件数与昏侧大致相当,午前时段明显多于子夜前时段.昏侧EMIC波高发生率与等离子体羽状结构有关,晨侧EMIC波高发生率与太阳风动压增强及稠密冷等离子体有关.晨侧-正午前EMIC波频率高于昏侧-子夜前,表明源区位置以及离子成分占比存在地方时差异.昏侧事件大多发生在早期恢复相,晨侧事件大多发生在晚期恢复相,晨-昏两侧的时间差异源于磁暴期间高能离子西向漂移所需时间及等离子体层顶位置的地方时差异.磁暴期间,EMIC波以H+波和He+为主,其中H+波主要分布在06:00 MLT—10:00 MLT(磁地方时)扇区,He+波主要分布在18:00 MLT—22:00 MLT扇区.在磁暴主相期间没有出现H+带波,但是出现He+-O+双波段EMIC波,表明磁暴主相期间环电流高浓度氧离子对H+带EMIC波具有抑制作用.By using high-resolution(50 Hz)magnetic field observations from Swarm constellation,the temporal and spatial characteristics of Electromagnetic Ion Cyclotron(EMIC)waves in different local time sectors at mid-latitudes are investigated during the magnetic storm period of 16-25 March 2015.There are comparable number of EMIC wave events in the dawn and dusk sectors,while there are more EMIC wave events in the pre-noon sector than in the pre-midnight sector.The duskside preference is related to the plasmaspheric plume,while the dawnside preference is related to the enhanced solar wind dynamic pressure and dense cold plasma.The wave frequency in the dawn and pre-noon sectors is higher than that in the dusk and pre-midnight sectors,implying the local time difference in the source location and the ion composition.Most of the duskside events occur in the early recovery phase,while the dawnside events occur in the late recovery phase.The time difference comes from the time required for the westward drift of energetic ions and local time difference in the plasmapause position.H+band waves are mainly found in the 06:00 MLT-10:00 MLT sector,while He+band waves are mainly confined in the 18:00 MLT-22:00 MLT sector.There is no H+band but a two band(He+and O+)EMIC wave during the storm main phase,indicating the role of the dense oxygen ion in inhibiting the H+band in the inner magnetosphere.

关 键 词：电磁离子回旋波 磁暴 太阳风动压 等离子体层羽状结构 

分 类 号：P353[天文地球—空间物理学]