Redefining the boundaries of interplanetary coronal mass ejections from observations at the ecliptic plane

TL;DR

This study analyzes a specific interplanetary coronal mass ejection (ICME) observed at L1, highlighting how compositional signatures and erosion processes define its boundaries and differ from magnetic cloud boundaries.

Contribution

It introduces a detailed analysis of ICME boundaries using compositional, magnetic, and kinematic data, emphasizing erosion and compositional signatures as key diagnostic tools.

Findings

Compositional signatures are effective in defining ICME boundaries.

Erosion at the front boundary explains differences between magnetic and compositional boundaries.

The event provides insights into ICME evolution and boundary identification.

Abstract

On 2015 January 6-7, an interplanetary coronal mass ejection (ICME) was observed at L1. This event, which can be associated with a weak and slow coronal mass ejection, allows us to discuss on the differences between the boundaries of the magnetic cloud and the compositional boundaries. A fast stream from a solar coronal hole surrounding this ICME offers a unique opportunity to check the boundaries' process definition and to explain differences between them. Using Wind and ACE data, we perform a complementary analysis involving compositional, magnetic, and kinematic observations providing relevant information regarding the evolution of the ICME as travelling away from the Sun. We propose erosion, at least at the front boundary of the ICME, as the main reason for the difference between the boundaries, and compositional signatures as the most precise diagnostic tool for the boundaries of ICMEs.