1
IZMIRAN, Troitsk,
Moscow Region, 142190, Russia
2
ISTP SD RAS,
Lermontov St. 126, Irkutsk, 664033, Russia
We analyze large-scale disturbances associated with extremely powerful flares and coronal mass ejections (CMEs) occurred during two passages across the solar disk of a grandiose complex of three active regions in October–November 2003 using SOHO/EIT imaging data. In particular, we study dimmings (i.e. transient coronal holes or regions of temporary depressions of the EUV emission) and, in a lesser degree, coronal waves (propagating emitting fronts). Our analysis is based on derotated fixed-difference heliograms, i.e., difference images in which the solar rotation is previously compensated with the same base pre-event frame being subtracted from all heliograms. Such a method allows us to consider both the 12-min interval heliograms at 195 Å and images observed in different-temperature bands of 171, 195, 284, and 304 Å produced with intervals of 6 hours. The analysis has revealed, in particular, that practically in all eruptive events during the both rotations, the CME-associated disturbances had a global character and covered almost the entire south hemisphere. At that, the northern hemisphere, where a large coronal hole was present, was faintly affected by the disturbances. The predominating dimmings on the disk were observed as narrow lengthy features basically stretching between three main remote active regions of the complex as well as a structure extended along a parallel in the southern polar sector. In events repeating with short time intervals, the main dimmings observed show clear homology by their form and location. In the course of the powerful event of 28 October, one homologous dimming system changed into another. Many dimmings manifested themselves by the same or similar appearance in the three coronal channels and in the transition-region line. It follows from the presented data that the same fast-recovered global structures at the coronal and transition-region levels were involved in the eruption processes of successive CMEs and the corresponding restructuring of the large-scale magnetic fields.