Numerical Simulation of Solar Magnetic Flux Emergence Using the AMR--CESE--MHD Code

TL;DR

This paper presents a numerical simulation of solar magnetic flux emergence using an advanced MHD code, reproducing key features of flux emergence and magnetic field restructuring relevant to solar eruptions.

Contribution

The study develops a new simulation framework for magnetic flux emergence from the solar interior to the corona using the AMR--CESE--MHD code, aligning with previous results but providing detailed insights into flux dynamics.

Findings

Flux tube rises driven by magnetic buoyancy.

Magnetic buoyancy instability triggers partial atmospheric entry.

Coronal magnetic field forms a sigmoid with a current layer.

Abstract

Magnetic flux emergence from the solar interior to the atmosphere is believed to be a key process of formation of solar active regions and driving solar eruptions. Due to the limited capability of observation, the flux emergence process is commonly studied using numerical simulations. In this paper, we developed a numerical model to simulate the emergence of a twisted magnetic flux tube from the convection zone to the corona using the AMR--CESE--MHD code, which is based on the conservation-element solution-element method with adaptive mesh refinement. The result of our simulation agrees with that of many previous ones with similar initial conditions but using different numerical codes. In the early stage, the flux tube rises from the convection zone as driven by the magnetic buoyancy until it reaches close to the photosphere. The emergence is decelerated there and with piling-up of the magnetic flux, the magnetic buoyancy instability is triggered, which allows the magnetic field to partially enter into the atmosphere. Meanwhile, two gradually separated polarity concentration zones appear in the photospheric layer, transporting the magnetic field and energy into the atmosphere through their vortical and shearing motions. Correspondingly, the coronal magnetic field has also been reshaped to a sigmoid configuration containing a thin current layer, which resembles the typical pre-eruptive magnetic configuration of an active region. Such a numerical framework of magnetic flux emergence as established will be applied in future investigations of how solar eruptions are initiated in flux emergence active regions.