Observations on a series of merging magnetic flux ropes within an interplanetary coronal mass ejection

TL;DR

This paper reports on the observation of merging magnetic flux ropes within an interplanetary coronal mass ejection, revealing internal reconnections that influence CME evolution and space weather forecasting.

Contribution

It provides the first detailed in-situ measurements of merging flux ropes within a CME, highlighting the role of internal reconnections in their evolution.

Findings

Magnetic flux ropes within a CME can merge through reconnection.

Merged flux ropes form larger-scale structures during propagation.

Rope interactions may affect space weather predictions.

Abstract

Coronal mass ejections (CMEs) are intense solar explosive eruptions. CMEs are highly important players in solar-terrestrial relationships, and they have important consequences for major geomagnetic storms and energetic particle events. It has been unclear how CMEs evolve when they propagate in the heliosphere. Here we report an interplanetary coronal mass ejection (ICME) consisting of multiple magnetic flux ropes measured by WIND on March 25-26, 1998. These magnetic flux ropes were merging with each other. The observations indicate that internal interactions (reconnections) within multi-flux-rope CME can coalesce into large-scale ropes, which may improve our understanding of the interplanetary evolution of CMEs. In addition, we speculated that the reported rope-rope interactions may also exist between successive rope-like CMEs and are important for the space weather forecasting.