The Driver of Coronal Mass Ejections in the Low Corona: A Flux Rope

TL;DR

This study shows that a hot flux rope acts as the primary driver of CME initiation and early acceleration, with its rise preceding the CME's leading front and flare onset, highlighting the flux rope's crucial role.

Contribution

It provides detailed observational evidence that pre-existing flux ropes drive CME formation and eruption, emphasizing their importance in CME dynamics.

Findings

Hot flux rope rises before CME leading front and flare onset.

Hot channel's speed exceeds that of the CME leading front.

Flux rope model accurately reproduces CME white-light images.

Abstract

Recent Solar Dynamic Observatory observations reveal that coronal mass ejections (CMEs) consist of a multi-temperature structure: a hot flux rope and a cool leading front (LF). The flux rope first appears as a twisted hot channel in the Atmospheric Imaging Assembly 94 A and 131 A passbands. The twisted hot channel initially lies along the polarity inversion line and then rises and develops into the semi-circular flux rope-like structure during the impulsive acceleration phase of CMEs. In the meantime, the rising hot channel compresses the surrounding magnetic field and plasma, which successively stack into the CME LF. In this paper, we study in detail two well-observed CMEs occurred on 2011 March 7 and 2011 March 8, respectively. Each of them is associated with an M-class flare. Through a kinematic analysis we find that: (1) the hot channel rises earlier than the first appearance of the CME LF and the onset of the associated flare; (2) the speed of the hot channel is always faster than that of the LF, at least in the field of view of AIA. Thus, the hot channel acts as a continuous driver of the CME formation and eruption in the early acceleration phase. Subsequently, the two CMEs in white-light images can be well reproduced by the graduated cylindrical shell flux rope model. These results suggest that the pre-existing flux rope plays a key role in CME initiation and formation.