Origin of Coronal Extreme Ultraviolet Shockwaves without a Coronal Mass Ejection Event
A leading theory of sunquake generation involves flare-accelerated particles depositing energy into the photosphere. Simulations of sunquake excitation suggest co-excitation with wavefronts propagating in the corona, similar to large-scale coronal propagating fronts (LCPFs), and also generate Moreton-Ramsey waves in the chromosphere. To investigate observational evidence for the particle-driven mechanism in LCPFs, we compare populations of events associated with and without coronal mass ejections (CMEs). CMEs are known to generate coronal shock waves also observed in EUV emission. We employ visual inspection of flare events that generate LCPFs using Atmospheric Imaging Assembly (AIA) and Large Angle and Spectrometric Coronagraph (LASCO) coronagraph images to find that the large-scale coronal waves associated with CMEs propagate noticeably faster. Then we examine standalone flare events (those that generate coronal waves without CMEs), using soft X-ray (SXR) data from the GOES satellite and focusing on characteristics related to magnetic energy release rate. This reveals that such standalone or confined flares differ from sunquake flares: they are less impulsive and energetic than sunquake flares. However, they are more impulsive but less energetic than LCPF-associated flares with a CME. In particular, coronal waves accompanied by CMEs exhibit significantly higher volume emission measures, suggesting a different generation mechanism.