Legolas: MHD spectroscopic analysis of the tearing mode
Date:
Contributed talk at CmPA Retrospective in honor of prof. Stefaan Poedts, Leuven, Belgium.
Abstract. The resistive tearing mode has been an active research topic since its discovery by Furth, Killeen and Rosenbluth in 1963, with renewed interest fuelled by its possibly key role in triggering magnetic reconnection. In turn, this magnetic reconnection can lead to eruptive events such as solar flares or the disruption of plasma confinement in tokamaks. However, the tearing mode growth rate is influenced by various other physical effects, such as the presence of a background flow, viscosity, or the Hall current. Using the modern linear 1D magnetohydrodynamic spectral code Legolas, all three effects can now be included in a tearing-unstable configuration to study their influence on the growth rate.
We present a parametric study exploring the influence of background flow on the tearing growth rate for two slab configurations: a rotating magnetic field of fixed size and a Harris sheet. Either configuration can be paired with various equilibrium flow profiles, where we differentiate between profiles with and without an inflexion point. We identify the relevant parameters, such as flow speed, plasma-\(\beta\), and the ratio of flow shear to magnetic shear.
It is also well-known that viscosity and the Hall current can introduce a non-negligible alteration to the tearing mode growth rate. Therefore, the Legolas code was extended to include both effects. We present the validation of this implementation and make some suggestions to map their effect on the tearing mode with Legolas.