Global Dynamics of Subsurface Solar Active Regions

TL;DR

This paper uses 3D numerical simulations to study the emergence and asymmetries of magnetic loops in the solar interior, revealing new magnetic structures and the effects of convection and rotation on active region formation.

Contribution

It introduces a self-consistent simulation approach to model magnetic loop emergence, highlighting the formation of magnetic necklaces and the influence of initial magnetic strength and convection.

Findings

Emergence of bipolar regions with spot-like features similar to solar observations

Identification of ring-shaped magnetic structures called 'magnetic necklaces'

Asymmetry of loop legs depends on initial magnetic field strength

Abstract

We present three-dimensional numerical simulations of a magnetic loop evolving in either a convectively stable or unstable rotating shell. The magnetic loop is introduced in the shell in such a way that it is buoyant only in a certain portion in longitude, thus creating an \Omega-loop. Due to the action of magnetic buoyancy, the loop rises and develops asymmetries between its leading and following legs, creating emerging bipolar regions whose characteristics are similar to the ones of observed spots at the solar surface. In particular, we self-consistently reproduce the creation of tongues around the spot polarities, which can be strongly affected by convection. We moreover emphasize the presence of ring-shaped magnetic structures around our simulated emerging regions, which we call "magnetic necklace" and which were seen in a number of observations without being reported as of today. We show that those necklaces are markers of vorticity generation at the periphery and below the rising magnetic loop. We also find that the asymmetry between the two legs of the loop is crucially dependent on the initial magnetic field strength. The tilt angle of the emerging regions is also studied in the stable and unstable cases and seems to be affected both by the convective motions and the presence of a differential rotation in the convective cases.