The issue of the influence of coronal holes (CHs) on coronal mass ejections (CMEs) in causing solar energetic particle (SEP) events is revisited.It is a continuation and extension of our previous work,in which no evident effects of CHs on CMEs in generating SEPs were found by statistically investigating 56 CME events.This result is consistent with the conclusion obtained by Kahler in 2004.We extrapolate the coronal magnetic field,define CHs as the regions consisting of only open magnetic field lines and perform a similar analysis on this issue for 76 events in total by extending the study interval to the end of 2008.Three key parameters,CH proximity,CH area and CH relative position,are involved in the analysis.The new result confirms the previous conclusion that CHs did not show any evident effect on CMEs in causing SEP events.
Cheng-Long ShenJia YaoYu-Ming WangPin-Zhong YeXue-Pu ZhaoShui Wang
Two interplanetary shocks are examined to determine the responses of the magnetic field and plasma in the plasma sheet upon the shock impacts by using TC-1 observational data.The two shocks are observed by WIND on November 7,2004.Prior to and after the shock,the IMF is either weakly southward or northward.The responses of the plasma sheet to the two shocks are intense and much similar.When the shock interacts with the magnetosphere,the magnetic field impulsively increases 1-2 min after the geomagnetic field sudden impulse (SI) judged from the Sym-H index change,and the magnetic field line is stretched.On the other hand,all of the ion density,the ion temperature,and the velocity of ion flow in the plasma sheet increase.Interestingly,quasi-periodical oscillations of the ion flow are suddenly enhanced,and the plasma flow is basically perpendicular to the local magnetic field.The responses of the magnetic field and the plasma are nearly simultaneous.The responses in the plasma sheet are probably caused by the lateral compression due to the dynamic pressure enhancement downstream the shock when the shock propagates antisunward in the magnetosheath.
