Magnetic thread twisting in a simulated solar atmosphere

Abstract

Context. Plasma inflows accompany a variety of processes in the solar atmosphere such as heating of coronal loops and formation of prominences. Aims. We model a stratified solar atmosphere, within which a simulated prominence thread experiences density accumulation via a plasma inflow designed to mimic the formation process. We aim to investigate the interaction of such a system with torsional perturbations, and the possible consequences. Methods. The linearised equations of motion and induction are integrated to analyse the spatial and temporal evolution of torsional perturbations that are randomly driven at the photospheric footpoints. Results. Our results demonstrate that magnetic threads will experience twist amplification. Different sources and sinks of energy and the corresponding amplification mechanisms are identified. Threads reaching chromospheric heights are most susceptible to magnetic twisting with the maximum twist occurring near their footpoints. The amplifying twists are associated with a standing wave behaviour along the simulated threads. Conclusions. Our work suggests that torsional perturbations may be amplified within prominence threads, with strong magnetic twists forming at the footpoints. The amplification process is facilitated by small length scales in the background magnetic field. On the other hand, a small length scale in the background density inhibits growth. Possible consequences of the amplified twists, including their role in supporting the dense plasma within a prominence structure are discussed.