Signatures of coronal mass ejections in differential emission measure analysis of the Sun as a star

TL;DR

This study demonstrates that coronal mass ejections produce detectable signatures in Sun-as-a-star differential emission measure data, with implications for remote CME detection and analysis.

Contribution

It shows that coronal dimmings associated with CMEs can be identified in Sun-as-a-star DEMs, highlighting the importance of considering the gradual phase in analysis.

Findings

All studied flares exhibited dimmings in EUV channels.

DEM decreases during dimmings in the temperature range $10^{5.7}-10^{6.3}$ K.

Gradual-phase correction enhances the detection of dimmings in DEMs.

Abstract

We investigated if signatures of coronal mass ejections (CMEs) can be retrieved in the differential emission measure (DEM) from Sun-as-a-star extreme-ultraviolet (EUV) observations. We analyzed 16 major, eruptive (i.e., associated with CMEs) flares. For each flare we constructed light curves of the average intensity of full-disk images taken by the SDO/AIA mission in EUV channels centered at 94, 131, 171, 193, 211, and 335 Angstrom. We also corrected the light curves for the flare gradual phase. From the analysis of the light curves we find that all the studied flares exhibit dimmings, where the intensity decreases with respect to the pre-flare phase, mainly in the 171, 193, and 211 Angstrom channels. The dimmings in these channels become more pronounced upon applying the gradual-phase correction. Calculation of the DEM from the six AIA EUV channels shows that during all the observed dimmings, the DEM decreases with respect to its value in the pre-flare phase in the temperature range $10^{5.7}-10^{6.3}$ K. The signature of the dimming is more pronounced in the range $10^{5.7}-10^{6.0}$ K for the DEMs calculated with the original light curves, and in the range $10^{6.0}-10^{6.3}$ K for the DEMs calculated by taking into account the gradual-phase correction. For a sample event, we also calculated DEMs from EVE and spatially resolved AIA observations of the source region to assess the impact of spectral resolution and full-disk averaging. For both these cases the temperature range where the dimming in the DEM is more pronounced is similar to that resulting from the analysis of the spatially averaged AIA data; the magnitude of the dimming is similar for the EVE and larger for the spatially resolved AIA observations. Coronal dimmings associated with CMEs can be detected in Sun-as-a-star DEMs. The flare gradual phase can lead to an underestimation of the magnitude of the dimming.