Solar Events During the STEREO-SOHO Quadrature

Between 2010 December and 2011 August the STEREO-A and B satellites were approximately at right angles to the SOHO satellite. This alignment was particularly advantageous for determining CME properties, since the closer a CME propagates to the plane of sky, the smaller the measurement inaccuracies are. Our primary goal was to study dimmings and their relationship to CMEs and flares during this time. We identified 53 coronal dimmings using STEREO/EUVI 195 Å observations, and linked 42 of the dimmings to CMEs (observed with SOHO/LASCO/C2) and 23 to flares. Each dimming in the catalog was processed with the Coronal Dimming Tracker (CoDiT) which detects transient dark regions in extreme ultraviolet images directly, without the use of difference images. This approach allowed us to observe footpoint dimmings: the regions of mass depletion at the footpoints of erupting magnetic flux rope structures. Our results show that the CME mass has a linear, moderate correlation with dimming total EUV intensity change, and a monotonic, moderate correlation with dimming area. Hence, the more the dimming intensity drops and the larger the erupting region is, the more plasma is evacuated. These results indicate that observing dimming properties has the potential to aid space weather forecasting efforts.