Twisted magnetic structures emerging from buoyancy instabilities

TL;DR

This paper investigates how buoyancy instabilities in sheared magnetic layers can generate large-scale helical magnetic structures that potentially rise through stellar convection zones to form active regions.

Contribution

It extends previous work by analyzing the interaction of two unstable magnetic zones, revealing how magnetic tension fosters the formation of large-scale helical structures.

Findings

Unstable top atmospheric layer leads to complex magnetic configurations.

Magnetic tension between layers promotes large-scale helical structures.

Results support the potential emergence of active regions from buoyancy instabilities.

Abstract

We here report calculations of magnetic buoyancy instabilities of a sheared magnetic layer where two separate zones are unstable. The idea is to study the possible generation of large-scale helical structures which could then rise through a stellar convection zone and emerge at the surface to create active regions. The calculations shown here are a follow-up of the work of Favier et al. (2012) where the instability developed in a weakly magnetized atmosphere, consisting of a uniform field oriented in a different direction from the unstable layer below. Here, the top layer representing the atmosphere is itself unstable to buoyancy instabilities and thus quickly creates a more complex magnetic configuration with which the layer below will interact. We also find in this case that the accumulation of magnetic tension between the two unstable layers favors the creation of large-scale helical structures.