Dynamo generated field emergence through recurrent plasmoid ejections

TL;DR

This study demonstrates that a large-scale dynamo-generated magnetic field can rise and form arch-like structures in the solar atmosphere without magnetic buoyancy, with recurrent plasmoid ejections observed in simulations.

Contribution

It introduces a novel simulation approach showing magnetic field emergence and plasmoid ejections driven by dynamo action without magnetic buoyancy.

Findings

Recurrent plasmoid ejections observed in the simulation.

Magnetic fields form twisted, arch-like structures in the upper layer.

Dynamo-generated fields can rise without magnetic buoyancy.

Abstract

Magnetic buoyancy is believed to drive the transport of magnetic flux tubes from the convection zone to the surface of the Sun. The magnetic fields form twisted loop-like structures in the solar atmosphere. In this paper we use helical forcing to produce a large-scale dynamo-generated magnetic field, which rises even without magnetic buoyancy. A two layer system is used as computational domain where the upper part represents the solar atmosphere. Here, the evolution of the magnetic field is solved with the stress--and--relax method. Below this region a magnetic field is produced by a helical forcing function in the momentum equation, which leads to dynamo action. We find twisted magnetic fields emerging frequently to the outer layer, forming arch-like structures. In addition, recurrent plasmoid ejections can be found by looking at space--time diagrams of the magnetic field. Recent simulations in spherical coordinates show similar results.