The Enhancement of the Energetic Particle Intensities in ICMEs

Abstract

The behavior of energetic particles in interplanetary coronal mass ejections (ICMEs) is of great interest. In general, due to the relatively closed magnetic structures of ICMEs, the energetic-particle intensities are usually depressed in them. However, previous studies have found some counterexamples. In this work, using protons with energies form ∼200 keV to ∼7 MeV observed by Wind/3dp as a measure, we check the proton intensity signatures of the 487 ICMEs between 1995 and 2017. A total of 12 ICMEs with extraordinary energetic-particle enhancements have been found, 9 of which are shock-interplanetary coronal mass ejection complex structures (S-ICMEs) and 3 that are isolated interplanetary coronal mass ejections (I-ICMEs). Comparing the two kinds of ICMEs, we find that energetic-particle intensities increase more in the S-ICMEs than in the I-ICMEs in all energy channels, especially in the high-energy channels. In addition, shocks inside energetic-particle-enhanced S-ICMEs are relatively fast and strong. These results indicate that shock-ICME interaction may be an effective local acceleration mechanism.