Coronal dimmings and what they tell us about solar and stellar coronal mass ejections

TL;DR

This review summarizes current knowledge on coronal dimmings, their relation to CMEs, and their potential as diagnostics for solar and stellar eruptions, including new categorization and stellar observations.

Contribution

It introduces a new physics-driven categorization of coronal dimmings and discusses their application to stellar CMEs, advancing understanding beyond previous reviews.

Findings

Coronal dimmings serve as footprints and indicators of CME mass loss.

A new categorization based on magnetic flux systems is proposed.

Recent stellar observations suggest dimmings can diagnose stellar CMEs.

Abstract

Coronal dimmings associated with coronal mass ejections (CME) from the Sun have gained much attention since the late 1990s when they were first observed in high-cadence imagery of the SOHO/EIT and Yohkoh/SXT instruments. They appear as localized sudden decreases of the coronal emission at extreme ultraviolet (EUV) and soft X-ray (SXR) wavelengths, that evolve impulsively during the lift-off and early expansion phase of a CME. Coronal dimmings have been interpreted as "footprints" of the erupting flux rope and also as indicators of the coronal mass loss by CMEs. However, these are only some aspects of coronal dimmings and how they relate to the overall CME/flare process. The goal of this review is to summarize our current understanding and observational findings on coronal dimmings, how they relate to CME simulations, and to discuss how they can be used to provide us with a deeper insight and diagnostics of the triggering of CMEs, the magnetic connectivities and coronal reconfigurations due to the CME as well as the replenishment of the corona after an eruption. In addition, we go beyond a pure review by introducing a new, physics-driven categorization of coronal dimmings based on the magnetic flux systems involved in the eruption process. Finally, we discuss the recent progress in studying coronal dimmings on solar-like and late-type stars, and to use them as a diagnostics for stellar coronal mass ejections and their properties.