Tangled Magnetic Fields in Solar Prominences

TL;DR

This paper investigates how tangled magnetic fields can support solar prominence threads, combining plasma dynamics, force-free models, and instability analysis to explain observed structures and densities.

Contribution

It introduces a comprehensive approach demonstrating that tangled magnetic fields can support prominence threads and explains their observed properties.

Findings

Tangled fields significantly reduce plasma flow velocities.

Magnetic pressure from tangled fields can support dense prominence threads.

Rayleigh-Taylor instability may explain the vertical thread structures.

Abstract

Solar prominences are an important tool for studying the structure and evolution of the coronal magnetic field. Here we consider so-called "hedgerow" prominences, which consist of thin vertical threads. We explore the possibility that such prominences are supported by tangled magnetic fields. A variety of different approaches are used. First, the dynamics of plasma within a tangled field is considered. We find that the contorted shape of the flux tubes significantly reduces the flow velocity compared to the supersonic free fall that would occur in a straight vertical tube. Second, linear force-free models of tangled fields are developed, and the elastic response of such fields to gravitational forces is considered. We demonstrate that the prominence plasma can be supported by the magnetic pressure of a tangled field that pervades not only the observed dense threads but also their local surroundings. Tangled fields with field strengths of about 10 G are able to support prominence threads with observed hydrogen density of the order of 10^(11) cm^(-3). Finally, we suggest that the observed vertical threads are the result of Rayleigh-Taylor instability. Simulations of the density distribution within a prominence thread indicate that the peak density is much larger than the average density. We conclude that tangled fields provide a viable mechanism for magnetic support of hedgerow prominences.