冕洞特征参数与重现型地磁暴关系的统计研究

在提取冕洞特征参数的基础上,利用1996年到2005年8月近十年来对地磁扰动有影响的356个冕洞事例,定量分析了冕洞特征参数(包括冕洞的面积比、经纬度跨度等)与冕洞高速流特征、重现型地磁扰动特征(包括扰动大小和持续时间等)之间的相关性,研究发现,从引起地磁扰动的冕洞在整个太阳活动周的分布来看,在地磁扰动峰年中冕洞影响同样具有重要的贡献;冕洞高速流太阳风速度与地磁扰动强度之间存在较强的相关性,而高速流中太阳风速度与冕洞面积比关系不大,与冕洞亮度存在一定相关性;冕洞的经度跨度与地磁扰动持续时间存在很强的正相关性. 

Primary Study About the Relationships Between Coronal Holes' Parameters and the Correlative Geomagnetic Disturbances

Data from the SOHO EIT284 images are used to analyze the development of coronal holes which existed from 1996 to 2005. In order to investigate the relationship between the coronal hole and earth effect, the correlativity of the coronal hole parameters including coronal holes＇ area and longitude span, with solar wind parameters and geomagnetic index were examined. Our investigation shows that: The correlation between coronal holes＇ longitude extend （20°N-20°S） and geomagnetic disturbance duration is very good. For coronal holes that appeared in 2002, the linear-correlation coefficient is 0.91, and for a long-lived recurrent coronal hole that existed for 15 Carrington rotations from 2002 to 2003, the Pearson Coefficient is 0.934. There is poor correlation between coronal holes＇ areas and maximum solar wind speed in the high speed stream. This result is different from the result that Nolte found in 1976. This might remind us that the solar wind speed in the high speed stream is not only related to the coronal holes＇ areas. The relationship between the high speed stream and the coronal hole must be much more complex. The correlations between the yearly averaged maximum solar wind speed in CHHSS （Coronal Hole-High Speed Stream） and the yearly averaged corresponding geomagnetic field index, for example, Ap index and Kp index are good, especially for the declining phase of solar activity cycle 23. But to the individual samples, fast velocity does not mean intense geomagnetic disturbance, which means that solar wind velocity is not the only major role that causes earth effect. From the study of a recurrent coronal hole that existed for fifteen Carrington rotations, we found that the daily average velocity maximum v^-max shows somewhat correlation to Kp maximum during the the geomagnetic disturbance. The linear-correlation coefficient is about 0.604.