低高度极尖区位形的经验模式  

Empirical model of the Earth's cusp at low-altitudes

作　　者：刘子谦 李晖 王赤 韩金鹏[3] 王江燕 Liu Ziqian;Li Hui;Wang Chi;Han Jinpeng;Wang Jiangyan(State Key Laboratory of Space Weather,National Space Science Center,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China;China Academy of Launch Vehicle Technology,Beijing 100076,China)

机构地区：[1]中国科学院国家空间科学中心空间天气学国家重点实验室,北京100190 [2]中国科学院大学,北京100049 [3]中国运载火箭技术研究院,北京100076

出　　处：《地球与行星物理论评（中英文）》2023年第4期466-475,共10页Reviews of Geophysics and Planetary Physics

基　　金：国家自然科学基金资助项目(42022032,41874203,42188101);科工局民用航天预先研究项目(D020301,D030202);中科院先导专项项目(XDA17010301);中国科学院国际伙伴计划资助项目(183311KYSB20200017);中国科学院前沿科学重点研究计划(QYZDJ-SSW-JSC028);国家重点实验室专项研究基金资助项目。

摘　　要：地球极尖区是太阳风等离子体进入内磁层和电离层的一个重要“窗口”,但其总体结构长期以来尚未确定.2008年3月8日两个连续亚暴期间,太阳风的整体变化范围较大,基于全球三维数值模拟我们建立了一个由行星际磁场(interplanetary magnetic field,IMF)B_(Y)、B_(Z)控制的低高度(1.1个地球半径高度)极尖区的预报模式.该模式由椭圆函数构造而成,拟合函数由极尖区位置和宽度控制并取决于IMF B_(Y)和B_(Z).极尖区地磁纬度(geomagnetic latitude,MLAT)随着向北IMF B_(Z)的增加而增加,随着向南IMF B_(Z)的增加而明显降低.当B_(Y)=0时,磁地方时(magnetic local time,MLT)接近12,当IMF为东向(西向)时,极尖区中心将位于北半球下午(上午)侧.MLAT宽度随IMF B_(Z)从北转南而减小,MLT宽度随IMF B_(Z)从北转南而增大.通过与DMSP卫星观测结果的比较分析,验证了该模型的有效性.基于低高度极尖区预报模式,将进一步建立极尖区三维预报模式,这将有助于空间天气预报.The Earth's cusp is a critical"window"for the solar wind plasma to enterthe low-altitude magnetosphere and ionosphere.However,the overall configuration of cusp has not been established.Based on the simulation of two successive substorms on 8 March 2008,we propose a 2D model of low-altitude(1.1 RE)cusp modulated by the interplanetary magnetic field(IMF)B_(Y) and B_(Z).This model is constructed from curve fitting of low-altitude cusp with an elliptic function controlled by the cusp center and width,which is dependent on IMF B_(Y) and B_(Z).The plasma thermal pressure PT derived from the simulation data is used to extract the cusp center on the sphere surface with a radius of 6 RE.The cusp center is defined as where PT reaches the maximum,and the cusp boundary is identified as where PT decreases to 68%of that at the cusp center.After the high-altitude cusp has been deter-mined,the low-altitude(0.1 RE altitude in the ionosphere)cusp can be obtained from mapping the high-altitude cusp along the magnetic field lines.The coordinate system of the low-altitude cusp used throughout this paper is the magnetic coordinate.The low-altitude cusp extracted from simulations is fitted with the elliptic function controlled by cusp location and width.The cusp geomagnetic latitude(MLAT)increases gradually with northward IMF B_(Z) but decreases significantly with southward IMF B_(Z).The local magnetic time(MLT)is nearly 12 when B_(Y)=0,corre-sponding to the observation results.When IMF B_(Y) is duskward(dawnward),the cusp center will locate at the post-noon(pre-noon)sector in the northern hemisphere.The MLAT width decreases as IMF B_(Z) swings from north to south,and the MLT width is the opposite.This model is validated by comparing with observations from DMSP satellites during this concerning time interval.Based on this 2D model of low-altitude cusp,the 3D cusp could be obtained further,which would help to space weather prediction.

关 键 词：极尖区 经验模式 太阳风 磁流体力学模拟 

分 类 号：P352[天文地球—空间物理学]