Characteristics of kinematics of a coronal mass ejection during the 2010 August 1 CME-CME interaction event

TL;DR

This study analyzes the interaction and kinematic behavior of two successive coronal mass ejections during the 2010 August 1 event, revealing how magnetic forces and drag influence their propagation and interaction in the solar wind.

Contribution

It provides a detailed reconstruction of CME kinematics during interaction, demonstrating the role of magnetic forces and drag in CME deceleration and merging.

Findings

CME2 decelerates significantly during interaction with CME1

Magnetic forces may enhance the deceleration of CME2

CME2 and CME1 merge and propagate as a single structure

Abstract

We study the interaction of two successive coronal mass ejections (CMEs) during the 2010 August 1 events using STEREO/SECCHI COR and HI data. We obtain the direction of motion for both CMEs by applying several independent reconstruction methods and find that the CMEs head in similar directions. This provides evidence that a full interaction takes place between the two CMEs that can be observed in the HI1 field-of-view. The full de-projected kinematics of the faster CME from Sun to Earth is derived by combining remote observations with in situ measurements of the CME at 1 AU. The speed profile of the faster CME (CME2; ~1200 km/s) shows a strong deceleration over the distance range at which it reaches the slower, preceding CME (CME1; ~700 km/s). By applying a drag-based model we are able to reproduce the kinematical profile of CME2 suggesting that CME1 represents a magnetohydrodynamic obstacle for CME2 and that, after the interaction, the merged entity propagates as a single structure in an ambient flow of speed and density typical for quiet solar wind conditions. Observational facts show that magnetic forces may contribute to the enhanced deceleration of CME2. We speculate that the increase in magnetic tension and pressure, when CME2 bends and compresses the magnetic field lines of CME1, increases the efficiency of drag.