地球磁层亚暴统计分析

利用AL和AE指数对第24个太阳活动周发生的亚暴事件进行统计分析.主要统计了关于磁层亚暴的强度，亚暴初值与恢复值的关系，亚暴持续时间，亚暴恢复相与增长相（包括膨胀相）持续时间的关系等.统计结果表明:在第24个太阳活动周中2008-2016年发生的亚暴事件大部分比较剧烈，其峰值大都在200～1200nT；初值和恢复值大都在30～100nT，并且事件占比符合正态分布；大部分亚暴都能恢复到亚暴初值60nT以内，并且差值越小，事件的占比越大.大部分亚暴的持续时间较长，在100～400min之间，其中增长相（包括膨胀相）持续时间均在120min以内，并且持续时间越长，其事件占比越小；大部分亚暴事件的恢复相持续时间在60～300min之间，并且呈现出正态分布特征.绝大多数亚暴事件的恢复相持续时间为增长相持续时间的10倍以下，其中约一半亚暴事件的恢复相持续时间为增长相持续时间的1～4倍.这说明亚暴的能量聚集速度约为能量释放速度的1～4倍.

Statistical Study on the Geomagnetic Substorm

The substorm is a process that releases enormous energy in the magnetosphere, including auroral, ionospheric, magnetospheric and thermospheric substorms. The substorm can result in severe disturbances in the whole magnetosphere and ionosphere. In this work, the AL and AE indices are employed to analyze the substorm events in the 24th solar cycle. Statistical analysis is performed on the relationship between the intensity of substorm, the initial value of substorm and the recovery value, the duration of a substorm, the relationship between substorm recovery phase and the duration of the growth phase (including expansion phase) and so on. The statistical results show that: most of the substorm events occurred in the 24th solar activity cycle from 2008 to 2016 are severe, with the peak value of the substorm mostly around 200～1200nT; the duration of most of the substorms ranges from 100 to 400min, the duration of the recovery phase of most of the substorms is between 60 to 300min, and presents the normal distribution characteristics; the recovery phase duration of most substorm events is less than 10 times of the growth phase duration. The statistical results on the substorm are helpful for further understanding of the occurrence and development of substorm in the magnetosphere. Therefore, it is of practical significance to further understand the energy evolution process in the magnetosphere.