The effect of artificial diffusivity on the flute instability

Sometimes, in order to improve the performance of magnetohydrodynamical codes, artificial diffusivity (D) is introduced in the mass continuity equation. In this communication, an analysis of the effect of the artificial diffusivity on the low-β plasma stability in a simple geometry is presented. It is shown that, at low diffusivity, one recovers classical results, whereas at high diffusivity the plasma becomes more unstable. Dependence of the stability on D is suppressed if the volume of the flux tube varies insignificantly in the course of the perturbation growth. These observations may help the code developers and users to identify the regimes where the artificial diffusivity is not affecting the results (or vice versa).