Comprehensive Characterization of the Dynamics of Two Coronal Mass Ejections in the Outer Corona

Abstract

Coronal mass ejections (CMEs) play a key role in determining space-weather conditions. Therefore, it is important to understand their evolution throughout the heliosphere. In this work, we carefully analyze the evolution of two kinematically different CMEs that erupted on 16 June 2010 and 14 June 2011, in a range of heliospheric distances of approximately 4 – 18 solar radii. From nearly simultaneous coronagraph images from the Solar-Terrestrial Relations Observatory and Solar and Heliospheric Observatory, we estimate the three- dimensional speed and acceleration–time profiles. We use these profiles to calculate the dynamic and thermodynamic parameters of the CMEs, such as the contribution of the forces and the polytropic index by means of the Flux Rope Internal State (FRIS) model, which as- sumes a self-similar evolution. We further test the validity of this assumption by comparing with observed quantities near the Sun and at 1 AU. We find that the kinematic properties of the two events differ in their evolution, which has an impact on the relative importance of the internal forces and on the thermodynamic quantities. In addition, our analysis reveals that the assumption of self-similar evolution is valid for the behavior in the middle corona for both events. At larger distances, however, this only holds for the 16 June 2010 event, which is significantly slower than the other.