The kink instability in force-free twisted flux tubes

This work investigates under which conditions a straight, highly magnetized flux tube with fieldlines frozen into perfectly conducting boundaries develops a kink instability when twisted. Running a force-free electrodynamics code, we conduct numerical experiments to vary the parameters with the most impact on stability: flux tube height and the amount of twist. Comparing the growth rate of the kink mode to analytical models, we then constrain an instability criterion. We identify a threshold of twist below which a flux tube remains in equilibrium. Past this threshold, progressive increases in the amount of twist cause the kink instability to develop sooner and grow faster. The force-free plasma flux tubes of this simulation have applications to high-energy, high-magnetization astrophysical phenomena, such as magnetar flares and accretion disc coronae variability.