http://arxiv.org/abs/2203.11887
We describe how analytic solutions for linear hydromagnetic waves can be used for testing cosmological magnetohydrodynamic (MHD) codes. We start from the comoving MHD equations and derive analytic solutions for the amplitude evolution of linear hydromagnetic waves in a matter-dominated, flat Einstein-de-Sitter (EdS) universe. The waves considered are comoving, linearly polarized Alfv\’en waves and comoving, magnetosonic (fast) waves modified by selfgravity. The solution for compressible waves is found for a general adiabatic index and we consider the limits of hydrodynamics without selfgravity in addition to the full solution. In addition to these analytic solutions, the linearized equations are solved numerically for a $\Lambda$CDM cosmology. We use the analytic and numeric solutions to compare with results obtained using the cosmological MHD code AREPO and find good agreement in all cases. We envision that our examples could be useful when developing a new cosmological MHD code or for regression testing of existing codes.
T. Berlok
Wed, 23 Mar 22
55/76
Comments: 19 pages, 9 figures, submitted to MNRAS, python code available at this https URL
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