亚暴等待时间的统计学分析:IMAGE卫星观测

STATISTICAL STUDY OF THE SUBSTORM WAIT TIME:IMAGE OBSERVATION

利用IMAGE卫星FUV极光图像数据,对北半球极光椭圆带2760个亚暴事件进行统计分析,得到亚暴等待时间的统计分布,并利用简单的数学模型对卫星轨道的影响进行了讨论,得到以下结论:(1)亚暴等待时间在2—3 h附近有一个峰值,较低纬度(MLat<65°)发生的亚暴事件,其等待时间略长于较高纬度(MLat≥65°)发生的亚暴事件;(2)较近磁尾(L<6 RE)发生的亚暴事件,其等待时间分布主要是高斯分布,较远磁尾(L≥6 RE)发生的亚暴事件,其等待时间分布是高斯和泊松分布的叠加,表明较近磁尾发生的亚暴事件比较远磁尾的亚暴事件更具有周期性;(3)卫星轨道的影响主要在10 h以后,对较近磁尾发生的亚暴事件的影响更大,造成8.5 h处伪峰值的出现。

This paper analyzes 2 760 substorm events in the Northern Hemisphere using observations made by the Far Ultraviolet Instrument onboard the IMAGE satellite to obtain the probability distribution of the substorm wait time（i.e.,the time interval between substorm onsets）.The effects of the satellite orbit are taken in account.It is found that（1） the most probable substorm wait time is between 2 and 3 hours.The wait time is longer for substorms occurring at lower latitudes than those occurring at higher latitudes（in the far tail）;（2） for substorms occurring in the near-Earth region,the wait time satisfies a Gaussian distribution,while for those in the far tail,the wait time satisfies both Gaussian and Poisson distributions,which may indicate that the near-Earth substorm events are more periodic than far-tail events;and（3） the satellite orbit affects the wait time distribution mainly after 10 hours,and causes one pseudo-peak at around 8 hours,which is more apparent in the lower-latitude events than in the higher-latitude events.