Flux emergence and coronal eruption

TL;DR

This study uses 3D MHD simulations to analyze flux emergence from the solar interior and the conditions leading to flux rope eruptions in the corona, aligning with observational data.

Contribution

It provides new insights into the magnetic flux distribution during flux emergence and the formation and eruption of flux ropes based on initial twist and ambient field strength.

Findings

Photospheric flux shows two opposite polarities with elongated tails.

Small initial twist results in undulating magnetic fields without tails.

A flux rope forms and can erupt depending on ambient magnetic field strength.

Abstract

Our aim is to study the photospheric flux distribution of a twisted flux tube that emerges from the solar interior. We also report on the eruption of a new flux rope when the emerging tube rises into a pre-existing magnetic field in the corona. To study the evolution, we use 3D numerical simulations by solving the time-dependent and resistive MHD equations. We qualitatively compare our numerical results with MDI magnetograms of emerging flux at the solar surface. We find that the photospheric magnetic flux distribution consists of two regions of opposite polarities and elongated magnetic tails on the two sides of the polarity inversion line (PIL), depending on the azimuthal nature of the emerging field lines and the initial field strength of the rising tube. Their shape is progressively deformed due to plasma motions towards the PIL. Our results are in qualitative agreement with observational studies of magnetic flux emergence in active regions (ARs). Moreover, if the initial twist of the emerging tube is small, the photospheric magnetic field develops an undulating shape and does not possess tails. In all cases, we find that a new flux rope is formed above the original axis of the emerging tube that may erupt into the corona, depending on the strength of the ambient field.