The tearing-thermal instability in coronal current sheets
Date:
Seminar at the Solar and Magnetospheric Theory Group, University of St Andrews, United Kingdom.
Abstract. In the solar corona, current sheets are unstable to both tearing and thermal instabilities. However, how the initial perturbation of such structures affects the time-scale to achieve the thermal runaway, is not well understood to date. Modelling a force-free Harris current sheet using both the magnetohydrodynamic spectroscopy code Legolas and non-linear simulation code MPI-AMRVAC, we explore both the linear and non-linear regime of this evolution. In the linear regime, part of the unstable thermal continuum adopts tearing properties, but it is not until the non-linear stage that a true thermal ‘runaway’ effect leads to condensations. Simulations initialised with the linear tearing or thermal modes were observed to reach the condensation stage faster than those initialised following standard practices, implying that perturbing an equilibrium current sheet with the fastest growing linear mode skips the mode mixing phase in which the dominant instability traditionally emerges. Consequently, this allows the simulation to enter the non-linear stage faster and reduces the computation time needed to reach the late-evolution stage.