Radiative Magnetohydrodynamic Simulation of the Confined Eruption of a Magnetic Flux Rope: Unveiling the Driving and Constraining Forces

TL;DR

This study uses 3D radiative MHD simulations to analyze the forces driving and constraining a confined magnetic flux rope eruption, revealing the roles of gravity, Lorentz force, and magnetic reconnection in the eruption dynamics.

Contribution

It provides a detailed analysis of the force balance and instability mechanisms governing confined flux rope eruptions in a realistic 3D RMHD framework.

Findings

Lorentz force triggers rapid acceleration after reaching torus instability threshold.

Magnetic reconnection enhances eruption feedback.

Gravity sustains the pre-eruptive flux rope stability.

Abstract

We analyse the forces that control the dynamic evolution of a flux rope eruption in a three-dimensional (3D) radiative magnetohydrodynamic (RMHD) simulation. The confined eruption of the flux rope gives rise to a C8.5 flare. The flux rope rises slowly with an almost constant velocity of a few km/s in the early stage, when the gravity and Lorentz force are nearly counterbalanced. After the flux rope rises to the height at which the decay index of the external poloidal field satisfies the torus instability criterion, the significantly enhanced Lorentz force breaks the force balance and drives rapid acceleration of the flux rope. Fast magnetic reconnection is immediately induced within the current sheet under the erupting flux rope, which provides a strong positive feedback to the eruption. The eruption is eventually confined due to the tension force from the strong external toroidal field. Our results suggest that the gravity of plasma plays an important role in sustaining the quasi-static evolution of the pre-eruptive flux rope. The Lorentz force, which is contributed from both the ideal magnetohydrodynamic (MHD) instability and magnetic reconnection, dominates the dynamic evolution during the eruption process.