Simulations of Emerging Magnetic Flux. I: The Formation of Stable Coronal Flux Ropes

TL;DR

This paper uses 3D MHD simulations to show how magnetic flux tubes emerging from the convection zone can form stable, non-neutralized coronal flux ropes influenced by pre-existing magnetic fields, relevant to understanding solar eruptions.

Contribution

It demonstrates that flux emergence can produce stable, non-current-neutralized coronal flux ropes tethered by overlying fields, expanding understanding of solar magnetic structures.

Findings

Emergence creates stable coronal flux ropes with net currents.

The height of flux ropes depends on the pre-existing dipole field strength.

Flux ropes are non-current-neutralized and stable, linked to CMEs.

Abstract

We present results from 3D visco-resistive magnetohydrodynamic (MHD) simulations of the emergence of a convection zone magnetic flux tube into a solar atmosphere containing a pre-existing dipole coronal field, which is orientated to minimize reconnection with the emerging field. We observe that the emergence process is capable of producing a coronal flux rope by the transfer of twist from the convection zone as found in previous simulations. We find that this flux rope is stable, with no evidence of a fast rise, and that its ultimate height in the corona is determined by the strength of the pre-existing dipole field. We also find that although the electric currents in the initial convection zone flux tube are almost perfectly neutralized, the resultant coronal flux rope carries a significant net current. These results suggest that flux tube emergence is capable of creating non-current-neutralized stable flux ropes in the corona, tethered by overlying potential fields, a magnetic configuration that is believed to be the source of coronal mass ejections.