Gradual Solar Coronal Dimming and Evolution of Coronal Mass Ejection in the Early Phase

TL;DR

This paper studies a two-stage coronal dimming event associated with a solar flare and CME, revealing a slow rise phase before eruption and a transition marked by rapid dimming and flare onset.

Contribution

It provides new insights into the early evolution of CMEs through detailed analysis of gradual and rapid dimming phases observed in solar eruptions.

Findings

Gradual dimming persists for over 30 minutes before flare onset.

Rapid dimming occurs simultaneously with flare initiation.

CME structure likely anchored at twin dimming regions undergoing slow rise.

Abstract

We report observations of a two-stage coronal dimming in an eruptive event of a two-ribbon flare and a fast coronal mass ejection (CME). Weak gradual dimming persists for more than half an hour before the onset of the two-ribbon flare and the fast rise of the CME. It is followed by abrupt rapid dimming. The two-stage dimming occurs in a pair of conjugate dimming regions adjacent to the two flare ribbons, and the flare onset marks the transition between the two stages of dimming. At the onset of the two-ribbon flare, transient brightenings are also observed inside the dimming regions, before rapid dimming occurs at the same places. These observations suggest that the CME structure, most probably anchored at the twin dimming regions, undergoes a slow rise before the flare onset, and its kinematic evolution has significantly changed at the onset of flare reconnection. We explore diagnostics of the CME evolution in the early phase with analysis of the gradual dimming signatures prior to the CME eruption.