2005年8月24日磁暴主相期间亚暴过程的多卫星联合观测分析  

Multi-satellite joint observations of an intense substorm during the main phase of 24 August,2005 storm

作　　者：孙晓英[1,2] 段素平[1] 刘维宁[1] 

机构地区：[1]中国科学院空间科学与应用研究中心,北京100190 [2]中国科学院大学,北京100049

出　　处：《地球物理学报》2014年第11期3729-3745,共17页Chinese Journal of Geophysics

基　　金：国家自然科学基金(40974099);国家重点实验室专项基金项目资助

摘　　要：本文根据OMNI、TC-2卫星、LANL系列卫星、Cluster星簇卫星(C1—C4)以及加拿大的8个中高纬地磁台站的观测数据,研究了2005年8月24日强磁暴(SYM-Hmin^-179nT)主相期间的强亚暴(ALmin^-4046nT)事件特征.该强磁暴在大振幅(IMF Bz min^-55.57nT)、短持续时间(~90min)的行星际磁场条件下产生,有明显的磁暴急始(SSC),强度较大且持续时间较短.发生在磁暴主相期间的亚暴发展的主要特征如下:亚暴增长相期间,C1—C4卫星先后穿越中心等离子体片;亚暴膨胀相触发后,在近地磁尾(X^-6RE)可观测到磁场偶极化现象;等离子体无色散注入区在亚暴onset开始后迅速沿经向扩展,但被限制在有限的经度范围;磁纬60°附近,Pi2地磁脉动振幅超过了100nT.膨胀相开始后,在中、高磁纬地磁台站可观测到负湾扰,近地磁尾可观测到Pi2空间脉动,中磁尾区域可观测到尾向流、磁重联以及O+/H+数密度比值在亚暴onset之后增大等现象.分析表明该强磁暴主相期间的强亚暴现象发生时序是自内向外:X^-6RE处TC-2观测到磁场偶极化(~09∶42∶30UT),同步轨道卫星LANL1994-084观测到等离子体无色散注入(~09∶44∶30UT),X^-17.8RE处C1观测到磁场重联(~09∶45∶30UT),由此推断该亚暴事件很可能是近地磁尾不稳定性触发产生,其发生区域距离地球很近.Observational data from OMNI, TC-2, LANL series of satellites, Cluster（C1--C4） and Canada＇s eight mid- and high-magnetic latitude geomagnetic stations are used to investigate the features of the intense substorm （ALmin ^--4046 nT ） during the main phase of the 24 August, 2005 storm （SYM-Hmin^-179 nT ）. The intense storm that occurred on 24 August, 2005 was driven by the interplanetary magnetic field with significantly negative Bz （IMF Bzmin~ --55.57 nT）, with a comparatively short duration （~90 rain ）. It had a significant storm sudden commence （SSC） and great intensity. The features of the intense substorm occurred during the main phase of the intense storm： during the growth phase, C1--C4 satellites were passing through the central plasma sheet. After expansion phase onset, in the near magnetotail （X --6RE）, magnetic field polarization was observed. Dispersionless Plasma injection zone extended rapidly along the longitude direction after the substorm onset, but was restricted to a limited longitude range. Near magnetic latitude 60°, the oscillation intensity of Pi2 geomagnetic pulsation was over 100 nT. After expansion phase onset, the mid- and high-magnetic latitude geomagnetic stations observed negative bays; in the near-Earth magnetotail, TC-2 observed Pi2 pulsations; in the mid-magnetotail, tailward flow and magnetic reconnection was observed and the ratio of O＋/ H＋ number density increased. Observational results show that the timing of the features of the intense substorm which occurred in the main phase of the intense storm was inside-out： at ~09 ： 42 ：30 UT, TC-2 observed magnetic field polarization at X^--6RE; at ~09 ：43：30 UT, LANL1994- 084 observed Plasma dispersionless injection; at ~09：45：30 UT, Cluster-1 observed magnetic reconnection at X^--17.8RE. Therefore, we inferred that this substorm event was likely to be triggered by some instabilities occurring in the near-Earth magnetotail, and its triggering region was ouite close to the Earth.

关 键 词：磁暴 亚暴 磁场偶极化 等离子体无色散注入 Pi2地磁脉动 

分 类 号：P353[天文地球—空间物理学]