  Magnetohydrodynamic (MHD) simulations of the solar corona have become more
popular with the increased availability of computational power. Modern
computational plasma codes, relying upon Computational Fluid Dynamics (CFD)
methods, allow for resolving the coronal features using solar surface
magnetograms as inputs. These computations are carried out in a full 3D domain
and thus selection of the right mesh configuration is essential to save
computational resources and enable/speed up convergence. In addition, it has
been observed that for MHD simulations close to the hydrostatic equilibrium,
spurious numerical artefacts might appear in the solution following the mesh
structure, which makes the selection of the grid also a concern for accuracy.
The purpose of this paper is to discuss and trade off two main mesh topologies
when applied to global solar corona simulations using the unstructured ideal
MHD solver from the COOLFluiD platform. The first topology is based on the
geodesic polyhedron and the second on UV mapping. Focus will be placed on
aspects such as mesh adaptability, resolution distribution, resulting spurious
numerical fluxes and convergence performance. For this purpose, firstly a
rotating dipole case is investigated, followed by two simulations using real
magnetograms from the solar minima (1995) and solar maxima (1999). It is
concluded that the most appropriate mesh topology for the simulation depends on
several factors, such as the accuracy requirements, the presence of features
near the polar regions and/or strong features in the flow field in general. If
convergence is of concern and the simulation contains strong dynamics, then
grids which are based on the geodesic polyhedron are recommended compared to
more conventionally used UV-mapped meshes.
