基于卫星观测的上游等离子体β与磁层顶厚度、速度等特征参数关系的统计研究  

A statistical study of the relationship between the upstream plasma β and characteristic parameters such as magnetopause thickness and velocity based on satellite observations

作　　者：李宏硕 吕建永 王明 袁换只 周悦 LI HongShuo;LU JianYong;WANG Ming;YUAN HuanZhi;ZHOU Yue(Institute of Space Weather,School of Math&Statistics,Nanjing University of Information Science&Technology,Nanjing 210044,China)

机构地区：[1]南京信息工程大学数学与统计学院空间天气研究所,南京210044

出　　处：《地球物理学报》2021年第9期3005-3020,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金(42030203,41974190,41604141)资助.

摘　　要：基于Cluster(C3)卫星的观测数据,本文统计分析了2001年至2009年的低纬(GSE坐标系下纬度小于45°)侧翼晨(磁地方时MLT<08)、昏(MLT>16)两侧磁层顶的特征.分别用法拉第残差最小化分析法(MFR分析)和DeHoffmann-Teller分析法(HT分析)计算了磁层顶厚度、运动速度以及平均电流密度等参数.收集了近磁层顶磁鞘侧的β值(等离子体热压磁压之比),并应用瓦伦测试划分了磁层顶的旋转不连续和切向不连续.结果表示,磁层顶的晨昏两侧存在明显的不对称,即晨侧磁层顶厚度更厚、运动也更加活跃.上游β值由近日侧到磁尾整体上表现出下降趋势,但在昏侧部分区域出现异常升高,通过分析β值对磁层顶厚度和运动速度的影响发现,更高的上游β值对应的磁层顶厚度更薄,运动速度更高,但是上游β的晨昏不对称并不是造成磁层顶厚度和运动速度晨昏不对称的主要原因,本文认为,磁层顶参数的晨昏不对称可能并不是由单一的上游参数造成的.最后,高β对研究区域内的磁层顶瓦伦关系有破坏作用.Based on satellite observations of Cluster(C3),this paper analyzes the crossing events of the low-latitude(less than 45°in the GSE coordinate system)dawn(magnetic local time MLT<08)and dusk(MLT>16)flanks of the magnetopause between 2001 and 2009.With“minimization of the Faraday residue”(MFR)and DeHoffmann-Teller analysis(HT),we calculate the thickness and motion of magnetopause,and the parameters such as average current density is given at the same time.The plasmaβ(the ratio of the plasma heat pressure and the magnetic pressure)in the magnetosheath and nearly the magnetopause is also collected.Applying to the Walén test,this paper divides the magnetopause into the rotation discontinuity and tangential discontinuity.The results show that there are obvious asymmetries on both flanks of the magnetopause and the dawn side magnetopause is thicker and more active.From nearly dayside region to the nearly magnetotail region,the upstreamβis decreasing,but there is an abnormal rising in partial regions of dusk side.Also,this paper find that the higher upstreamβvalue corresponds to the thinner and more active magnetopause,but the upstreamβis not the main reason of the asymmetry between the both sides,It is suggested that the asymmetries of the magnetopause may not be caused by a single upstream parameter.Finally,highβcan destroy the magnetopause Walén relation in the study area.

关 键 词：磁层顶参数 等离子体β 磁层顶晨昏不对称 

分 类 号：P353[天文地球—空间物理学]