Observational evidence of CMEs interacting in the inner heliosphere as inferred from MHD simulations

TL;DR

This paper presents MHD simulation results showing how multiple CMEs interact in the inner heliosphere, highlighting observable signatures like shock merging and brightness increases, aiding interpretation of multi-spacecraft observations.

Contribution

The study provides the first detailed simulation-based analysis of CME interactions in the inner heliosphere, linking observational signatures to physical processes.

Findings

Large temperature increases in the sheath indicate shock merging.

Brightness enhancements in coronagraph images signal CME interactions.

Multiple spacecraft observations are crucial for understanding CME dynamics.

Abstract

The interaction of multiple Coronal Mass Ejections (CMEs) has been observed by LASCO coronagraphs and by near-Earth spacecraft, and it is thought to be an important cause of geo-effective storms, large Solar Energetic Particles events and intense Type II radio bursts. New and future missions such as STEREO, the LWS Sentinels, and the Solar Orbiter will provide additional observations of the interaction of multiple CMEs between the Sun and the Earth. We present the results of simulations of two and more CMEs interacting in the inner heliosphere performed with the Space Weather Modeling Framework (SWMF). Based on those simulations, we discuss the observational evidence of the interaction of multiple CMEs, both in situ and from coronagraphs. The clearest evidence of the interaction of the CMEs are the large temperature in the sheath, due to the shocks merging, and the brightness increase in coronagraphic images, associated with the interaction of the leading edges. The importance of having multiple satellites at different distances and angular positions from the Sun is also discussed.