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 1930UT 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.