Confined Flares in Solar Active Region 12192 from 2014 October 18 to 29

TL;DR

This study analyzes the magnetic and flare activities of solar active region 12192 during October 2014, revealing mechanisms behind homologous flares, jet-associated flares, and the region's limited CME production due to magnetic confinement.

Contribution

It provides detailed observational insights into the magnetic configurations and flare mechanisms in AR 12192, highlighting the role of magnetic flux motions and overlying field strength.

Findings

Homologous flares had similar structures and triggering mechanisms.

Most flares were confined with limited CME activity due to magnetic field constraints.

Jet-associated flares involved flux cancellation at jet footpoints.

Abstract

Using the observations from the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO), we investigate six X-class and twenty-nine M-class flares occurring in solar active region (AR) 12192 from October 18 to 29. Among them, thirty (including six X- and twenty-four M-class) flares originated from the AR core and the other five M-flares appeared at the AR periphery. Four of the X-flares exhibited similar flaring structures, indicating they were homologous flares with analogous triggering mechanism. The possible scenario is: photospheric motions of emerged magnetic fluxes lead to shearing of the associated coronal magnetic field, which then yields a tether-cutting favorable configuration. Among the five periphery M-flares, four were associated with jet activities. The HMI vertical magnetic field data show that the photospheric fluxes of opposite magnetic polarities emerged, converged and canceled with each other at the footpoints of the jets before the flares. Only one M-flare from the AR periphery was followed by a coronal mass ejection (CME). From October 20 to 26, the mean decay index of the horizontal background field within the height range of 40-105 Mm is below the typical threshold for torus instability onset. This suggests that a strong confinement from the overlying magnetic field might be responsible for the poor CME production of AR 12192.