极区场向电子事件持续时间的统计研究

Statistical Study on Duration of the Field-aligned Electron Events in the Polar Region

利用Cluster卫星的4s分辨率数据,对极区高高度4～8Re范围内的场向电子事件进行了统计,分析了场向电子事件持续时间的分布特性,并研究了不同地磁条件下场向电子事件持续时间的分布.结果表明：极区高高度范围场向电子事件的持续时间为6 ～ 475 s,大部分场向电子的持续时间小于50 s,在持续时间10～ 20 s内,场向电子事件最容易发生；持续时间长的场向电子在北半球上行的情况下发生较多；持续时间较长的场向电子事件一般都发生在地磁场By较小的条件下.

Using the data （with 4s resolution） from Cluster satellites, the field-aligned electron events at high- altitude 4 -8Re of the polar region are analyzed statistically. The distribution of the duration of field-aligned elec- trons and the relationship between the duration and geomagnetic field-By component are studied. The result shows that the range of the duration is about 6 - 475 seconds. A majority of the field-aligned electron events are shorter than 50 seconds, and the most number of field-aligned electron events happened with the duration of about 10 - 20 seconds. Long duration of field-aligned electron events mostly occurred in the Northern Hemisphere with up-flowing movement. The long-time field-aligned electron events can be found during quiet geomagnetic field By component, but the occurrence of the short-time field-aligned electron events has be independent of geomagnetic filed By compo- nent.