第23和24太阳活动周高纬地磁感应电流分布特性

基于高纬度芬兰Mäntsälä地区近两个太阳活动周期（1999—2017年）天然气传输管道的地磁感应电流（GIC，I_GIC）观测数据，统计研究了GIC扰动的分布特征以及强GIC扰动与磁暴和地磁亚暴的相关性.研究发现:95.83%时间段的GIC强度分布在0～1A之间.定义:若某个时间段|I_GIC|_max> 1A，则认为发生GIC扰动；|I_GIC|_max>10A，则认为发生强GIC扰动事件.GIC扰动在磁地方时夜侧附近发生的概率最高，这主要与地磁亚暴发生期间电离层电流最剧烈的变化发生在磁地方时夜侧附近有关；强GIC扰动经常爆发式出现，且都发生在磁暴期间，但大多数磁暴并不伴随强GIC扰动事件发生.磁暴急始驱动的强GIC扰动事件较少，由磁层压缩引起地磁场突然增强驱动的强GIC扰动事件持续时间较短；强GIC扰动事件主要发生在磁暴主相和恢复相，由环电流变化驱动的强GIC扰动事件一般持续时间较长且强度较大. 

Distribution Characteristics of the Geomagnetic Induced Currents at High Latitude during Solar Cycle 23 and 24

Based on the data of the Geomagnetic Induced Currents (GIC, I_GIC) in the natural gas transmission pipelines in the high-latitude Mäntsälä area, Finland, from 1999 to 2017 during the recent two solar cycles. The distribution characteristics of GIC disturbances and the relationship between strong GIC disturbances and magnetic storms and substorms are analyzed. It is found that for 95.83% of the data points, the GIC intensity was distributed between 0A and 1A. The occurrence probability of GIC disturbance defined as |I_GIC|_max>1A, is highest near the nightside in MLT, which is possibly related to the stronger ionosphere current disturbances during the magnetospheric substorm at the nightside. All the intense GIC disturbances defined as the events with |I_GIC|_max>10A are accompanied by geomagnetic storms. Strong GIC disturbance events mainly occur in the main phase and the recovery phase of the magnetic storms, which are driven by ring current enhancement and have a longer time-duration and greater intensity. On the other hand, there are also a few events with a much shorter duration occurring with the storm sudden commencement. These events are caused by the sudden compression of the magnetosphere.