Evolution and Consequences of Interacting CMEs of 9 - 10 November 2012 Using STEREO/SECCHI and In Situ Observations

Abstract

Understanding the kinematic evolution of coronal mass ejections (CMEs) in the heliosphere is important to estimate their arrival time at Earth. The kinematics of CMEs can change when they interact or collide with each other as they propagate in the heliosphere. In this article, we analyze the collision and post-interaction characteristics of two Earth-directed CMEs that were launched successively on 9 and 10 November 2012. To do this, we used white-light imaging observations from STEREO/SECCHI and in situ observations taken from the Wind spacecraft. We tracked two density-enhancement features associated with the leading and trailing edge of the 9 November CME and one density enhanced feature associated with the leading edges of the 10 November CME by constructing J-maps. We found that the leading edge of the 10 November CME interacted with the trailing edge of the 9 November CME. We also estimated the kinematics of these features of the CMEs and found a significant change in their dynamics after interaction. In in situ observations, we identified distinct structures associated with interacting CMEs and also observed heating and compression as signatures of their interaction. Our analysis shows an improvement in the arrival-time prediction of CMEs when their post-collision dynamics are used instead of the pre-collision dynamics. By estimating the true masses and speeds of these colliding CMEs, we investigated the nature of the observed collision, which is found to be almost perfectly inelastic. The investigation also places in perspective the geomagnetic consequences of the two CMEs and their interaction in terms of occurrence of geomagnetic storms and triggering of magnetospheric substorms.