日冕物质抛射的磁绳正演法及源区投影修正方法的讨论

摘要

In this paper, the three-dimension velocity of 21 well-structured Corona Mass Ejections (CMEs) were obtained by Forward Modeling based on STEREO-SECCHI observations during 2007-2008. By measuring the height of the projected front in STEREO-A and STEREO-B sky plane and using the projection modified method, modified velocities of these CME, which were treated as 3D velocity before, were also obtained. Comparing the 3D velocity obtained from the Forward Modeling method and the modified velocity, it is found that the 3D velocity and the modified velocity are almost the same when angular distance, which is defined as the angle between the line connecting CME source region and Sun center and the line connecting observer and Sun center, is greater than 50°; that when the angular distance is less than 50°, the difference is obvious. The latter result shows that the modified method can not be used for the CMEs with angular distance less than 50°. It is found that the projected velocity is almost the same as the 3D velocity when the angular distance is greater than 65°. This result implies that the CME event with angular distance larger than 65°could be treated as a limb event.%利用磁绳正演法(forward modeling)研究了2007-2008年STEREO卫星观测到的21个结构清晰的日冕物质抛射(CME)事件,得到这些CME事件在三维空间的运动速度;与根据STEREO A星和B星观测速度进行源区投影修正得到的结果进行比较,发现这种源区投影修正方法存在很大的局限性.统计结果表明,当CME源区在日面上的日心角距(CME源区和日心连线与观测点和日心连线的夹角)大于50°时,修正速度与三维速度之间的差别不大;当日心角距小于这个值时,修正速度与三维速度差别明显,尤其对于小日心角距,相差甚大.统计结果还表明,当日心角距大于65°时,A星和B星得到的投影速度与三维速度相近,投影速度可以作为CME的三维速度.