Mechanism of spontaneous formation of stable magnetic structures on the Sun

TL;DR

This study uses realistic 3D MHD simulations to reveal how stable magnetic structures like sunspots and pores spontaneously form on the Sun through vortex interactions and merging of small-scale magnetic filaments.

Contribution

It demonstrates a two-step process of magnetic self-organization leading to stable structures, advancing understanding of solar magnetic phenomena.

Findings

Magnetic structures form from small-scale filaments associated with vortices.

Merging of filaments due to vortex attraction creates large-scale stable magnetic features.

Simulated magnetic structures reach strengths of 1.5 kG at the surface and 6 kG internally.

Abstract

One of the puzzling features of solar magnetism is formation of long-living compact magnetic structures; such as sunspots and pores, in the highly turbulent upper layer of the solar convective zone. We use realistic radiative 3D MHD simulations to investigate the interaction between magnetic field and turbulent convection. In the simulations, a weak vertical uniform magnetic field is imposed in a region of fully developed granular convection; and the total magnetic flux through the top and bottom boundaries is kept constant. The simulation results reveal a process of spontaneous formation of stable magnetic structures, which may be a key to understanding of the magnetic self-organization on the Sun and formation of pores and sunspots. This process consists of two basic steps: 1) formation of small-scale filamentary magnetic structures associated with concentrations of vorticity and whirlpool-type motions, and 2) merging of these structures due to the vortex attraction, caused by converging downdrafts around magnetic concentration below the surface. In the resulting large-scale structure maintained by the converging plasma motions, the magnetic field strength reaches ~1.5 kG at the surface and ~6 kG in the interior; and the surface structure resembles solar pores. The magnetic structure remains stable for the whole simulation run of several hours with no sign of decay.