Dynamic Coupling of Convective Flows and Magnetic Field during Flux Emergence

TL;DR

This study uses advanced magnetohydrodynamic simulations to explore how convective flows influence magnetic flux emergence and sunspot formation, revealing the importance of large-scale convection and horizontal flows in magnetic energy transfer.

Contribution

It introduces a realistic simulation model incorporating radiative cooling and ionization to analyze flux emergence and magnetic coupling in the solar atmosphere.

Findings

Large-scale convection is crucial for sunspot formation.

Horizontal flows prevent polarities from separating.

Magnetic energy is injected and transported during flux emergence.

Abstract

We simulate the buoyant rise of a magnetic flux rope from the solar convection zone into the corona to better understand the energetic coupling of the solar interior to the corona. The magnetohydrodynamic model addresses the physics of radiative cooling, coronal heating and ionization, which allow us to produce a more realistic model of the solar atmosphere. The simulation illustrates the process by which magnetic flux emerges at the photosphere and coalesces to form two large concentrations of opposite polarities. We find that the large-scale convective motion in the convection zone is critical to form and maintain sunspots, while the horizontal converging flows in the near surface layer prevent the concentrated polarities from separating. The foot points of the sunspots in the convection zone exhibit a coherent rotation motion, resulting in the increasing helicity of the coronal field. Here, the local configuration of the convection causes the convergence of opposite polarities of magnetic flux with a shearing flow along the polarity inversion line. During the rising of the flux rope, the magnetic energy is first injected through the photosphere by the emergence, followed by energy transport by horizontal flows, after which the energy is subducted back to the convection zone by the submerging flows.