Authors: K. Dissauer (NWRA), G. Barnes (NWRA), KD Leka (NWRA and Nagoya University / ISEE), Eric Wagner (NWRA)

Reported small-scale activity that occurs before the sudden onset of solar eruptive events involves, in general, transient brightenings (TBs) in EUV and soft X-rays that result from plasma heating and particle acceleration, flows of hot plasma along coronal loops and pre-event coronal dimmings (PCDs) indicating early filament activation or the rise of overlying field enabling a coronal mass ejection (CME) to subsequently occur.  The roles of such precursors, mostly reported in single event case studies, in the initiation and early evolution of solar flares and CMEs is still not fully understood. Whether these phenomena primarily occur during the pre-event phase of an active region’s evolution is not clear.

In this contribution we investigate the uniqueness and causal relationship of precursor activity to solar flares and CMEs for a statistically significant sample.  The signatures’ temporal behavior, photospheric magnetic context, coronal dynamics, and temperature and density prior to events is analyzed and compared against the characteristics of similar phenomena during activity-quiet epochs (i.e., testing uniqueness). We also check if pre-event activity occurs at locations favorable to reconnection (locations of open field, magnetic null points etc.) as determined by the topology of a Potential Field Source Surface model (i.e., testing causal relationship).  Archive data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO), specifically EUV time-series images and vector magnetograms are used and preliminary results will be presented.

The importance of the outcome of this work is two-fold: if uniqueness/causal relationship can be proven the results should bring us one step closer to understanding which, and when, proposed triggering mechanisms succeed. If pre-event TBs and PCDs cannot be differentiated from random brightenings and dimmings they are physically not involved in the event initiation.

This material is based upon work supported by NASA/80NSSC21K0738 and the NSF AGS-ST/2154653.