Tests of Dynamical Flux Emergence as a Mechanism for CME Initiation

TL;DR

This study uses 2.5D simulations to evaluate the role of dynamical flux emergence in CME initiation, revealing that most shear magnetic energy remains confined to the lower atmosphere and does not lead to eruptions.

Contribution

It demonstrates the limited transfer of shear magnetic energy into the corona during flux emergence, challenging assumptions in existing CME models that neglect this process.

Findings

Less than 10% of magnetic energy in the corona is shear field.

Coronal flux ropes formed do not erupt due to confined shear energy.

Flux emergence alone is insufficient to trigger CMEs in the modeled scenarios.

Abstract

Current coronal mass ejection (CME) models set their lower boundary to be in the lower corona. They do not calculate accurately the transfer of free magnetic energy from the convection zone to the magnetically dominated corona because they model the effects of flux emergence using kinematic boundary conditions or simply assume the appearance of flux at these heights. We test the importance of including dynamical flux emergence in CME modeling by simulating, in 2.5D, the emergence of sub-surface flux tubes into different coronal magnetic field configurations. We investigate how much free magnetic energy, in the form of shear magnetic field, is transported from the convection zone to the corona, and whether dynamical flux emergence can drive CMEs. We find that multiple coronal flux ropes can be formed during flux emergence, and although they carry some shear field into the corona, the majority of shear field is confined to the lower atmosphere. Less than 10% of the magnetic energy in the corona is in the shear field, and this, combined with the fact that the coronal flux ropes bring up significant dense material, means that they do not erupt. Our results have significant implications for all CME models which rely on the transfer of free magnetic energy from the lower atmosphere into the corona but which do not explicitly model this transfer. Such studies of flux emergence and CMEs are timely, as we have new capabilities to observe this with Hinode and SDO, and therefore to test the models against observations.