冕洞特征参数与地磁暴强度及发生时间统计

Statistical Study between Characteristic Parameters of Coronal Holes and Intensity/Time of Geomagnetic Storms

地磁暴是空间天气预报的重要对象.在太阳活动周下降年和低年,冕洞发出的高速流经过三天左右行星际传输到达地球并引发的地磁暴占主导地位.目前地磁暴的预报通常依赖于1AU处卫星就位监测的太阳风参数,预报提前量只有1h左右.为了增加地磁暴预报提前量,需要从高速流和地磁暴的源头即太阳出发,建立冕洞特征参数与地磁暴的定量关系.分析了2010年5月到2016年12月的152个冕洞-地磁暴事件,利用SDO/AIA太阳极紫外图像提取了两类冕洞特征参数,分析了其与地磁暴期间ap,Dst和AE三种地磁指数的统计关系,给出冕洞特征参数与地磁暴强度以及发生时间的统计特征,为基于冕洞成像观测提前1~3天预报地磁暴提供了依据.

Geomagnetic storm is an important subject in space weather forecasting.High speed solar wind originating from coronal holes passes through the interplanetary space about three days before reaching the Earth.It triggers geomagnetic storms which are dominant during the declining phase and the minimum year of a solar cycle.At present,geomagnetic storms forecasting mostly relies on solar wind parameters at 1 AU,and geomagnetic storms are predicted in advance only by about 1 hour.In order to predict geomagnetic storms much earlier,it is necessary to establish the quantitative relationship between the characteristic parameters of coronal holes and geomagnetic storms from the point of the Sun,which is the source of high speed solar wind and geomagnetic storm.In this study,152 coronal holes and relevant geomagnetic storms events from May 2010 to December 2016 are analyzed.Two characteristic parameters of coronal holes are extracted based on SDO/AIA images,and the geomagnetic index ap,Dst and AE during geomagnetic storms are analyzed.The statistical relationship between characteristic parameters of coronal holes and intensity/time of geomagnetic storms is established,which provides a basis for predicting geomagnetic storms in advance by 1~3 days based on solar EUV images.