The Kinetic Evolution Course across Interplanetary Shocks

Abstract:

An interesting physical phenomenon often occurs when coronal mass ejections (CMEs) interact with each other, i.e., a shock overtakes, penetrates and then interacts with a preceding CME. Interplanetary shocks can accelerate, compress, and heat the preceding ejecta. The interaction between the preceding ejecta and shock also results in variations in the shock strength and geometric structure. So far, there are numerous investigations at the kinetic level about the bow shock and interplanetary shocks propagating ahead of the interplanetary CMEs (ICMEs), however, the investigations about the interplanetary shocks propagating in the ICMEs have been relatively rare. As a result of this, we propose to analyze two interplanetary shocks(for comparative purpose) which propagated in and ahead of ICMEs using the in situ measurements from the Wind satellite(WIND/MFI，WIND/SWE，WIND/3DP) at kinetic level, respectively. In this study, we present the observations of two shock events mentioned above and the analyses mainly include several aspects shown as below.

(1)Determine the shock events associated with the ICMEs, confirm the boundaries of the ICMEs and analyze the in situ observation features of the ICMEs;(2)Identify the impact on the electron distribution in the ICMEs of the shocks propagating in the ICMEs and try to give reasonable physical explanations;(3)Recognize the reflection courses of the shock events through ion distribution functions near the shock events; (4)Obtain information on the heating process of the electrons and ions across the shock and try to confirm the heating mechanism;(5)Perform power spectral and polarization analysis for the shocks and sheaths and get the wave mode information for the shock events;(6)Organize the above results and try to find the associations between them.

The results reveal that ambient background of the shocks can greatly affect the shock kinetic courses and the heating capacity of the shocks, which offers new insights into collisionless shock dissipation. What’s more, we can get a more comprehensive knowledge about the shock physics by comparing the results of the ICME shocks mentioned here and the results of bow shock in the future, which is beneficial for the space weather predictions.