Coronal Dimming Diagnostics for Stellar CMEs: Contrasting CMEs and Confined Flares

Candidate events on stars, supported by clear events on the Sun, suggest “coronal dimming” signals may be a powerful way to study coronal mass ejections (CMEs) across a range of stars. However, magnetically confined events can also produce signals that resemble CME-induced dimming, complicating identification. Here, we present modeling and observational analysis of both confined and eruptive events on the Sun to quantitatively compare dimming morphology and evolution. We show that eruptive events preferentially produce deeper, longer-lived, and more spatially extended dimmings, whereas confined flares tend to yield weaker, shorter-lived, and more localized signatures. Using the newly developed SPECTRUM code, we synthesize EUV/UV spectra to identify features that distinguish eruptive from confined cases. We then extend these results to stellar scenarios, identifying challenges and recommending solutions for using coronal dimming to detect stellar CMEs. With insights from models validated with detailed solar observations, we argue that it is possible to use coronal dimming as a reliable indicator of stellar CMEs.