Magnetic Reconnection at Hyperbolic Flux Tube associated with a Confined Flare in NOAA Active Region 12268

TL;DR

This study combines magnetic field extrapolation and data-constrained MHD simulation to analyze magnetic reconnection at hyperbolic flux tubes during a confined solar flare in NOAA AR 12268, revealing the primary role of HFT reconnection.

Contribution

It introduces a comprehensive approach integrating non-force-free extrapolation and MHD simulation to investigate HFT reconnection in a confined flare.

Findings

Reconnection occurs at the HFT above the flaring region.

Slipping reconnection is observed at QSL footpoints.

HFT reconnection drives flare brightenings and ribbons.

Abstract

In this paper, we identify the magnetic reconnections at the hyperbolic flux tube (HFT), aided by slipping reconnection at quasi-separatrix layers (QSLs), which are pivotal to the occurrence of a confined M2.1 class flare in NOAA active region 12268. The magnetic field topology before the flare's onset is obtained through a non-force-free-field extrapolation scheme that accommodates a non-zero Lorentz force. A key aspect is the presence of an HFT in the computational domain above the flaring region, along with two QSLs at the lower boundary. To simulate the dynamics of the active region, we conduct a data-constrained magnetohydrodynamics (MHD) simulation initiated by the extrapolated field. The dynamics captured in the simulation document the formation of a current sheet within the HFT configuration, leading to magnetic reconnection at the HFT. Additionally, we observe the slipping motion of the footpoints of the magnetic field lines in the QSLs at the bottom boundary, which indicates the occurrence of slipping reconnection in the QSLs. Importantly, the magnetic reconnection at the HFT is suggested to be the primary driver in the development of the intricate flare brightenings and the flare ribbons.