Initialising non-linear simulations with linear eigenmodes
Date:
Contributed talk at the National Astronomy Meeting 2024 (Modern methods and numerical approaches for analysing the Sun’s dynamic atmosphere), Kingston upon Hull, United Kingdom.
Abstract. When non-linear simulations start from an equilibrium configuration, it is common practice to add an arbitrary perturbation at the initial time to kick off the evolution. Generally, it is argued that the exact form of the perturbation does not matter because the non-linear evolution mixes all linear eigenoscillations. To verify this claim, we use the Legolas code, which computes the linear eigenmodes of a given one-dimensionally varying equilibrium, to compute the natural oscillations of two unstable equilibria: a velocity-sheared fluid interface and a Harris current sheet. Next, several linear solutions and superpositions thereof are inserted as initial perturbations in non-linear simulations with MPI-AMRVAC. The resulting time evolutions are analysed and compared to identify the role of the initial perturbation.