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

TL;DR

This study analyzes small-scale moving intensity enhancements in solar active regions using EUV imaging from SDO/AIA and Hi-C 2.1, identifying distinct groups of these features with characteristic velocities near the coronal sound speed.

Contribution

It introduces a Gaussian mixture model to classify and analyze different groups of active region moving campfires (ARMCs) based on their physical characteristics.

Findings

Multiple ARMC groups identified with distinct intensity and velocity profiles.

ARMC velocities are near the coronal sound speed, differing from Alfvénic jets.

Cross-validation confirms the existence of these groups across datasets.

Abstract

The small-scale moving intensity enhancements remotely observed in the extreme ultraviolet images of the solar active regions, which we refer to as active region moving campfires (ARMCs), are related to local plasma temperature and/or density enhancements. Their dynamics is driven by the physical processes in the entire coronal plasma. Our previous study of ARMCs indicates that they have characteristic velocities at around the background sound speed. The main goal of our work is to carry out a simultaneous analysis of EUV images from two observational missions, SDO/AIA and Hi-C 2.1. The aims of the performed cross-validating analysis of both SDO/AIA and Hi-C 2.1 data were to reveal how the observed moving features are distributed over the studied active region, AR12712, test the existence of different groups of ARMCs with distinct physical characteristics. We use the statistical model of intensity centroid convergence and tracking that was developed in our previous paper. Furthermore, a Gaussian mixture model fit of the observed complex of moving ARMCs is elaborated to reveal the existence of distinct ARMC groups and to study the physical characteristics of these different groups. In data from the 171\AA, 193\AA\ and 211\AA\ channels of SDO/AIA, we identified several groups of ARMCs with respect to both blob intensity and velocity profiles. The existence of such groups is confirmed by the cross-validation of the 172\AA\ data sets from Hi-C 2.1. The ARMCs studied in this paper have characteristic velocities in the range of the typical sound speeds in coronal loops. Hence, these moving objects differ 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). The nature of the discovered statistical grouping of the ARMC events is not known.