Evolution of an arched magnetized laboratory plasma in a sheared magnetic field

TL;DR

This study experimentally investigates how magnetic field configurations influence the shape and stability of arched magnetized plasmas, providing insights relevant to solar atmospheric phenomena.

Contribution

It presents new experimental data on the effects of overlying and guiding magnetic fields on arched plasma structures in a laboratory setting.

Findings

Increased overlying magnetic field enhances plasma writhe.

Orientation of guiding magnetic field determines S-shape of plasma.

Plasma remains below kink instability threshold.

Abstract

Arched magnetized structures are a common occurrence in space and laboratory plasmas. Results from a laboratory experiment on spatio-temporal evolution of an arched magnetized plasma ($\beta \approx 10^{-3}$, Lundquist number $\approx 10^{4}$, plasma radius/ion gyroradius $\approx 20$) in a sheared magnetic configuration are presented. The experiment is designed to model conditions relevant to the formation and destabilization of similar structures in the solar atmosphere. The magnitude of a nearly horizontal overlying magnetic field was varied to study its effects on the writhe and twist of the arched plasma. In addition, the direction of guiding magnetic field was varied to investigate its role in formation of either forward- or reverse-S shaped plasma structures. The electrical current in the arched plasma was well below the current required to make it kink unstable. A significant increase in the writhe of the arched plasma was observed with larger magnitudes of overlying magnetic field. Forward-S shaped arched plasma was observed for a guiding magnetic field oriented nearly anti-parallel to the initial arched plasma current, while the parallel orientation yielded the reverse-S shaped arched plasma.