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The Lyman-alpha (Ly{\alpha};1216 {\AA}) line is the brightest emission linein the quiescent solar spectrum and radiates a significant fraction of theavailable nonthermal energy during flares. Despite its importance, there is alack of detailed studies of Ly{\alpha} spectral variability during flares.Recently, spectrally resolved Ly{\alpha} flare observations from theSORCE/SOLSTICE instrument have become available. This study examines Ly{\alpha}spectral variability and its relationship with HXR emission from nonthermalelectrons, using observations of two M-class flares from SORCE/SOLSTICE andRHESSI. Imaging observations from STEREO/SECCHI EUVI and SDO/AIA providefurther context. Enhancements across the Ly{\alpha} line profile were found toclosely correlate with bursts of HXR emission, suggesting a primarilynonthermal origin. Red enhancement asymmetries at the peak of each flare wereattributed to chromospheric evaporation, while blue wing enhancement and blueasymmetry were linked to a bright filament-eruption seen in SDO/AIA 1600 {\AA}images. These findings contribute to the understanding of spectral Ly{\alpha}variability during flares and highlight the need for future studies using ahigher quality and quantity of spectral Ly{\alpha} flare observations. Suchstudies will further characterise the physical mechanisms driving Ly{\alpha}flare variability.

Spectral Irradiance Variability in Lyman-Alpha Emission During Solar Flares