Calliope: Pseudospectral shearing magnetohydrodynamics code with a pencil decomposition

Abstract: The pseudospectral method is a highly accurate numerical scheme suitable for turbulence simulations. We have developed an open-source pseudospectral code, \textsc{\textsf{Calliope}}, which adopts the P3DFFT library \citep{Pekurovsky2012} to perform a fast Fourier transform with the two-dimensional (pencil) decomposition of numerical grids. \textsc{\textsf{Calliope}} can solve incompressible magnetohydrodynamics (MHD), isothermal compressible MHD, and rotational reduced MHD with parallel computation using very large numbers of cores ($> 10^5$ cores for $2048^3$ grids). The code can also solve for local magnetorotational turbulence in a shearing frame using the remapping method \citep{Rogallo1981,Umurhan2004}. \textsc{\textsf{Calliope}} is currently the only pseudospectral code that can compute magnetorotational turbulence using pencil-domain decomposition. This paper presents the numerical scheme of \textsc{\textsf{Calliope}} and the results of linear and nonlinear numerical tests, including compressible local magnetorotational turbulence with the largest grid number reported to date.