磁尾爆发性整体流和地磁Pi2脉动关系研究

利用Cluster,TC-1以及中国和欧洲在中低纬六个地面台站的数据,分析了2004年10月22日1700—1930UT发生的三次BBF事件过程中地面和近地空间磁场脉动的特性.这三次BBF事件都发生在地磁活动的平静时期.结果发现,有两次平静时期的BBF确实对应着阻尼型Pi2脉动,并且脉动的特征与以前观测结果中的特征类似.在第一次BBF事件中,空间观测和地面观测均发现了Pi2脉动;在第二次事件中,地面观测到了Pi2脉动,而空间没有观测到Pi2脉动;在第三次事件中,空间和地面观测都没有发现Pi2脉动.这些观测事实说明BBF所激发的Pi2脉动特征是相当复杂的,而且并不是所有BBF都能产生Pi2脉动,所以到底BBF在什么条件下可以产生Pi2仍然是一个没有解决的问题.

Relations Between Magnetotail BBF and Pi2 Pulsations

Recent observations show that there is a close correlation between BBFs (bursty bulk flows) and mid-low latitude Pi2 pulsations.However the relation between BBFs and Pi2 pulsations remains an unsettled open question.In this paper,by using the data of Cluster,TC-1/DSP and six ground stations (Dedu,Taian,Kashi from China and Castello Tesino,Ranchio,Nagycenk from Europe),three BBF events were analyzed that occurred during magnetic quiet times from 1700 UT to 1930 UT on October 22,2004.It is found that two of BBF events can excite Pi2s.The P.i2s appeared simultaneously The Pi2s in H components at six ground stations have almost the same starting time,same period (about 60 s) and same waveform.The characteristics of relevant Pi2s are consistent with those of cavity mode.For the first BBFs,TC-1 inside the plasmasphere observed a Pi2 event.However for the second BBF,TC-1 did not observe any Pi2 signature.During the third BBF event,both ground and space observations show that there are no Pi2s.Thus it can be concluded that not all BBFs can excite Pi2s.What kind of BBFs can excite the Pi2 remains an open question.