Greatorex, Harry J. ; Milligan, Ryan O. ; Dammasch, Ingolf E.

published in Solar Physics, 299 issue 162 (2024)

Abstract: Despite the energetic significance of Lyman-alpha (Lyα; 1216 Å) emission from solar flares,regular observations of flare related Lyα have been relatively scarce until recently. Advances in instrumental capabilities and a shift in focus over previous solar cycles mean it is now routinely possible to take regular co-observations of Lyα emission in solar flares. Thus, it is valuable to examine how the instruments selected for flare observations may influence the conclusions drawn from the analysis of their unique measurements. Here, we exam- ine three M-class flares each observed in Lyα by GOES-14/EUVS-E, GOES-15/EUVS- E, or GOES-16/EXIS-EUVS-B, and at least one other instrument from PROBA2/LYRA, MAVEN/EUVM, ASO-S/LST-SDI, and SDO/EVE-MEGS-P. For each flare, the relative and excess flux, contrast, total energy, and timings of the Lyα emission were compared between instruments. It was found that while the discrepancies in measurements of the relative flux between instruments may be considered minimal, the calculated contrasts, excess fluxes, and energetics may differ significantly – in some cases up to a factor of five. This may have a notable impact on multi-instrument investigations of the variable Lyα emission in solar flares and estimates of the contribution of Lyα to the radiated energy budget of the chro- mosphere. The findings presented in this study will act as a guide for the interpretation of observations of flare-related Lyα from upcoming instruments during future solar cycles and inform conclusions drawn from multi-instrument studies.

DOI: 10.1007/s11207-024-02407-7