Transport in the interplanetary medium of coronal mass ejections

Abstract

Coronal mass ejections (CMEs) are large scale structures of plasma and magnetic field expelled from the Sun to the interplanetary medium and generally observed in white light coronagraphs. During their travel, in the interplanetary medium these structures named interplanetary coronal mass ejections (ICMEs), suffer acceleration or deceleration due to the interaction with the ambient solar wind. This process can be understood as a transference of momentum between the interplanetary CME (ICME) and the solar wind. This process seems to be fundamentally different for 'slow' and 'fast' ICMEs (compared with the ambient solar wind velocity).
In this work, we approach the problem from the fluid dynamics point of view and consider the ICMEs – solar wind system as two interacting fluids under the action of viscous forces. We note that this interaction is a special case of interaction between low density plasmas. Using these viscous forces in the Newtons Second Law, we obtained an analytical solution for the ICME velocity as a function of time. By comparing our analytic results with empirical models found in recent literature, we suggested values for the viscosity and drag parameters in this system. In this first approximation we have neglected the magnetic field.