Quasi-synchronism of bursts in solar coronal structures in the Mg XII 0.84-nm line from CORONAS-F/SPIRIT experimental data

Abstract

Based on CORONAS-F/SPIRIT images of the Sun in the MgXII 0.84-nm line, we have performed photometric measurements and investigated the time dependence of the surface brightness for fragments of ten active regions. Continuous observations were carried out on March 3–4, 2002, for about 19 h when the satellite moved in shadowless orbits. The interval between the images was, on average, about 1 min. A time correlation has been found between the brightness variations in some pairs of high-temperature regions spaced from 10° to 106° apart. We have analyzed the statistical characteristics of the temporal distribution of bursts: the observed nonuniformity of the distribution was found to be impossible for a random Poisson process. To identify sympathetic (induced) bursts, we have studied the connections in the form of magnetic loops between active regions using CORONAS-F/SPIRIT and SOHO/EIT solar images. The most probable delays between events (X-ray bursts) in various active regions have been estimated. By assuming that the disturbance propagates along the coronal loops connecting active regions, we have estimated the propagation velocity of the disturbance, ∼1700 km s−1. In the period under study, the active regions in which a large number of bursts were observed lay along the periphery of a developing equatorial coronal hole. We have concluded that the simultaneous emergence of new magnetic fluxes in the photosphere was responsible for most of the quasi-synchronous events on March 3–4, 2002. We have calculated the physical conditions in coronal loops by assuming that the propagation of magnetohydrodynamic waves in the corona could be responsible for the appearance of connected events.