A Numerical Simulation on the Solar-Terrestrial Transit Time of Successive CMEs during November 4-5, 1998

Abstract

The solar-terrestrial transit process of three successive coronal mass ejections (CMEs) during November 4-5, 1998 has been investigated numerically in one-dimensional spherical geometry. These CMEs interact with each other while they are propagating in interplanetary space and finally form a “Complex Ejecta”. A Harten's total variation diminishing (TVD) scheme is applied to solve magnetohydrodynamic (MHD) equations numerically, starting from an ambient solar wind equilibrium, with appropriate dimensionless gravity parameter α, plasma beta β, and gas polytropic index γ The equilibrium is consistent in solar wind speed υr, proton number density Np, and the ratio of proton thermal pressure to magnetic pressure βp with the observation of ACE spacecraft at Lagrange point (L1). Merely velocity pulse is introduced in the numerical computation, whose amplitude and duration are determined by observation data of Lasco/C2, GOES, LEAR combined with CME's “Cone Model” proposed by Michalek et al. The results show that the differences of two shock arrival times (SATs) between the numerical calculation and ACE observation are 3 and 4 hours respectively. Therefore the numerical model proposed in this paper can estimate SAT and rough shock intensity formed by successive CMEs evolving in interplanetary space and suggests a potential application in SAT prediction for space weather.