On the Nature of the Three-part Structure of Solar Coronal Mass Ejections

TL;DR

This paper challenges traditional views on the three-part structure of CMEs, proposing a new explanation supported by observations and a survey, emphasizing its fundamental role in understanding CME physics.

Contribution

It introduces a novel interpretation of CME structures, supported by a detailed event analysis and a comprehensive survey, redefining the nature of the three-part CME appearance.

Findings

CME front originates from plasma pileup along magnetic arcades

The bright core is a hot-channel magnetic flux rope

The dark cavity is a low-density zone between the CME front and the MFR

Abstract

Coronal mass ejections (CMEs) result from eruptions of magnetic flux ropes (MFRs) and can possess a three-part structure in white-light coronagraphs, including a bright front, dark cavity and bright core. In the traditional opinion, the bright front forms due to the plasma pileup along the MFR border, the cavity represents the cross section of the MFR, and the bright core corresponds to the erupted prominence. However, this explanation on the nature of the three-part structure is being challenged. In this paper, we report an intriguing event occurred on 2014 June 14 that was recorded by multiple space- and ground-based instruments seamlessly, clearly showing that the CME front originates from the plasma pileup along the magnetic arcades overlying the MFR, and the core corresponds to a hot-channel MFR. Thus the dark cavity is not an MFR, instead it is a low-density zone between the CME front and a trailing MFR. These observations are consistent with a new explanation on the CME structure. If the new explanation is correct, most (if not all) CMEs should exhibit the three-part appearance in their early eruption stage. To examine this prediction, we make a survey study of all CMEs in 2011 and find that all limb events have the three-part feature in the low corona, regardless of their appearances in the high corona. Our studies suggest that the three-part structure is the intrinsic structure of CMEs, which has fundamental importance for understanding CMEs.