Comparison of the Hall Magnetohydrodynamics and Magnetohydrodynamics evolution of a flaring solar active region

TL;DR

This study compares Hall magnetohydrodynamics (HMHD) and MHD simulations of a solar flare, finding HMHD better reproduces observed features such as faster reconnection, magnetic field line rotation, and plasma dynamics.

Contribution

It demonstrates that HMHD simulations provide a more accurate representation of solar flare magnetic reconnection and plasma behavior than traditional MHD models.

Findings

HMHD supports faster magnetic reconnection.

HMHD shows better agreement with observed flare ribbon locations.

Plasma rotation observed in HMHD matches chromospheric observations.

Abstract

This work analyzes the Hall magnetohydrodynamics (HMHD) and magnetohydrodynamics (MHD) numerical simulations of a flaring solar active region as a testbed while idealizing the coronal Alfv\'en speed to be of two orders of magnitude lesser. HMHD supports faster magnetic reconnection and shows richer complexity in magnetic field line evolution compared to the MHD. The magnetic reconnections triggering the flare are explored by numerical simulations augmented with relevant multi-wavelength observations. The initial coronal magnetic field is constructed by non-force-free extrapolation of photospheric vector magnetic field. Magnetic structure involved in the flare is identified to be a flux rope, with its overlying magnetic field lines constituting the quasi-separatrix layers (QSLs) along with a three-dimensional null point and a null line. Compared to the MHD simulation, the HMHD simulation shows a higher and faster ascend of the rope together with the overlying field lines, which further reconnect at the QSL located higher up in the corona. The foot points of the field lines match better with the observations for the HMHD case with the central part of the flare ribbon located at the chromosphere. Additionally, field lines are found to rotate in a circular pattern in the HMHD, whereas no such rotation is seen in the MHD results. Interestingly, plasma is also observed to be rotating in a co-spatial chromospheric region, which makes the HMHD simulation more credible. Based on the aforementioned agreements, HMHD simulation is found to agree better with observations and, thus, opens up a novel avenue to explore.