行星际激波对地球磁层的压缩效应分析

Compression Effects of Interplanetary Shock to the Magnetosphere

2004年11月9日WIND飞船探测到一个典型的行星际激波.激波前行星际磁场为持续约50 min的弱南向磁场,越过激波面,磁场发生北向偏转且太阳风动压脉冲增强.在此强动压脉冲增强结构作用下,磁层被压缩至一个很小的区域.激波作用于磁层时引起地球同步轨道各区域高能粒子通量的响应,但是不同磁地方时的高能粒子通量的响应不同,表现出双模式扰动,即在晨昏两侧各能段的电子和质子通量显著增强,在子夜侧发生类似于亚暴的无色散粒子注入现象.扰动从向阳面传输到背阳面,向阳面粒子通量最先增强,随后背阳面靠近晨昏两侧,粒子通量开始增强,最后子夜侧粒子通量表现出无色散高能粒子注入的特点.另外,在靠近正午侧,质子通量先于电子通量发生响应,在子夜侧电子通量则先于质子通量发生响应.利用位于向阳面正午两侧的GOES-10和GOES-12卫星观测数据发现,激波作用于磁层时靠近晨侧的磁场变化表现出简单压缩效应,而靠近昏侧的磁场变化则显然不同,B_x分量减弱,B_z分量几乎减为零,而B_y分量则显著增强.此外,位于近地磁尾低纬尾瓣区的TC-1卫星观测到激波触发的尾瓣SI现象.

On November 9,2004,the WIND spacecraft detected a typical interplanetary shock.Before the shock,there is a sustaining weak southward magnetic field lasting about 50 min.Across the shock front,the magnetic field turns northward,and the solar wind dynamic pressure is abruptly enhanced, i.e.,the shock is a strong Dynamic Pressure Pulse（DPP）.The magnetosphere is compressed to a rather small region upon the impact of the DPP.During the impingement of the shock,the magnetospheric compression causes two-mode disturbances of the energetic particle at the geosyn- chronous orbit,i.e.,particle flux enhancement due to the compression near dawn and dusk and dispersionless particle injection similar to substorm.The disturbances propagate from the dayside to the nightside.The energetic particle fluxes on the dayside first increase,and then after about 1 min, the particle fluxes near dawn and dusk on the nightside begin to increase.Finally,dispersionless particle injection is seen near the midnight.Furthermore,near the noon the responses of electron are prior to those of proton.Contrarily,near the midnight the responses of proton are prior to those of electron.By using GOES-10 and GOES-12 observations on two sides of the noon,it is found that the magnetic field on the dawn-noon sector is simply compressed,while for the magnetic field on the noon-dusk sector,B_x and B_z component decreases,but B_y component notably increases.The TC-1 spacecraft located at near-Earth low-latitude lobe region observes the shock-induced lobe SI phenomena.