MHD simulation of the formation and propagation of multiple magnetic clouds in the heliosphere

School of Earth & Space Sci., Univ. of Sci. & Tech. of China, Hefei, Anhui 230026, PR China e-mail: ymwang@ustc.edu.cn

Received: 6 June 2004
Accepted: 22 November 2004

Abstract

A multiple-magnetic-cloud (Multi-MC) structure formed by the overtaking of two successive coronal mass ejections (CMEs) in the heliosphere is studied by using a 2.5-D MHD simulation. This simulation illustrates the process of the formation and propagation of two identical CMEs, which are ejected with speeds of 400 km s^-1 and 600 km s^-1 respectively and initially separated by 12 h. The results show that it takes ~18 h for the fast cloud to catch up with the preceding slow one, then the two clouds form a Multi-MC structure that arrives at 1 AU three days later. The fast cloud is slowed down significantly because of the blocking by the preceding slow one. This implies that the travel time of a Multi-MC structure is dominated by the preceding slow cloud. Moreover, most primary observational characteristics of Multi-MC at 1 AU are well represented by the simulation. In addition, by combining observations, theoretical model and the simulation results, differences between Multi-MC and other types of in-situ observed double-flux-rope structure are addressed. A comparison of Multi-MC to coronal-mass-ejection cannibalization near Sun is also given.