Categorization model of moving small-scale intensity enhancements in solar active regions

Context. The small-scale moving intensity enhancements remotely observed in the EUV images of the solar active regions manifest the physical processes that provide necessary conditions for the local plasma temperature and/or density enhancements and their acceleration. Earlier studies indicate that the characteristic velocities of these motions value at around the background sound speed. Understanding the dynamical and statistical properties of the mentioned transient phenomena is the scope of the present paper. Aims. The main goal of this work is to carry out a simultaneous analysis of SDO/AIA and Hi-C 2.1 EUV images, in a similar manner as Williams et al. (2020). In our case we use the statistical model of centroid convergence and tracking in active regions developed in our previous paper. The aim of the cross-validating analysis of data from two observational missions was to reveal how the observed moving features are distributed in active regions and to perform statistical hypothesis test on whether groups of flows with similar physical characteristics exist. Methods. The methodology comprises the above-mentioned model of intensity enhancement tracking. Furthermore, Gaussian mixture models are fit to the discovered Active Region Moving Campfires (ARMCs) to reveal groups of observed events and study some of their physical characteristics. Results. In data from the 171 Å, 193 Å and 211 Å channels of SDO/AIA, we identified several groups with respect to both blob intensity and velocity profiles. The physical presence of such groups is justified by the cross validation of the 172 Å datasets of Hi-C 2.1 observational mission. Conclusions. The ARMCs studied in this paper have characteristic velocities in a range that contains the typical sound speeds in loops. Hence, these moving objects di er from the well-known rapid Alfv´enic velocity jets from magnetic reconnection sites. This is also proven by the fact that ARMCs propagate along the active region magnetic structure (strands). This origin of the discovered groups of events is not known to us and it requires further theoretical studies and modeling.

Publication year:2022

Accessibility:Open