Numerical Simulations of Chromospheric Microflares

TL;DR

This study uses 2.5D resistive MHD simulations considering gravity, ionization, and radiation to model chromospheric microflares, revealing how temperature enhancement depends on magnetic field and resistivity, and establishing a scaling law.

Contribution

It introduces a comprehensive 2.5D MHD simulation framework for chromospheric microflares that accounts for multiple physical effects and derives a new scaling law relating temperature increase to physical parameters.

Findings

Temperature enhancement is sensitive to background magnetic field.

Total evolution time depends on anomalous resistivity.

A scaling law relates temperature increase, time, density, magnetic field, and resistivity.

Abstract

With gravity, ionization, and radiation being considered, we perform 2.5D compressible resistive MHD simulations of chromospheric magnetic reconnection using the CIP-MOCCT scheme. The temperature distribution of the quiet-Sun atmospheric model VALC and the helium abundance (10%) are adopted. Our 2.5D MHD simulation reproduces qualitatively the temperature enhancement observed in chromospheric microflares. The temperature enhancement $\Delta T$ is demonstrated to be sensitive to the background magnetic field, whereas the total evolution time $\Delta t$ is sensitive to the magnitude of the anomalous resistivity. Moveover, we found a scaling law, which is described as $\Delta T/\Delta t \sim {n_H}^{-1.5} B^{2.1} {\eta_0}^{0.88}$. Our results also indicate that the velocity of the upward jet is much greater than that of the downward jet and the X-point may move up or down.