131 and 304 {\AA} Emission Variability Increases Hours Prior to Solar Flare Onset

Abstract

Thermal changes in coronal loops are well-studied, both in quiescent active regions and in flaring scenarios. However, relatively little attention has been paid to loop emission in the hours before the onset of a solar flare; here, we present the findings of a study of over 50 off-limb flares of GOES class C5.0 and above. We investigated the integrated emission variability for Solar Dynamics Observatory Atmospheric Imaging Assembly channels 131, 171, 193, and 304 \r{A}ngstroms for 6 hours before each flare, and compared these quantities to the same time range and channels above active regions without proximal flaring. We find significantly increased emission variability in the 2-3 hours before flare onset, particularly for the 131 and 304 channels. This finding suggests a potential new flare prediction methodology. The emission trends between the channels are not consistently well-correlated, suggesting a somewhat chaotic thermal environment within the coronal portion of the loops that disturbs the commonly-observed heating and cooling cycles of quiescent active region loops. We present our approach, the resulting statistics, and discuss the implications for heating sources in these pre-flaring active regions.