Simulation of MHD for space weather on locally-refined cubed-sphere grids using Proto

A key component of an integrated solar wind simulation capability is that of solving the magnetohydrodynamics equations in a spherical annulus with boundary conditions specified on the inner surface. We describe here a new algorithm and software framework for such problems. The key algorithmic components are: (1) the use of a cubed-sphere coordinate system to represent the spherical annulus without pole singularities; (2) fourth-order finite-volume discretizations of the MHD equations on mapped-multiblock grids that conform to the cubed-sphere coordinates; and (3) the use of structured-grid adaptive mesh refinement to concentrate computational effort in regions requiring greater accuracy / resolution. We are implementing this code using Proto, a new high-level library for representing structured-grid calculations that hides the tedious details of writing high-performance code on GPUs. We will present some preliminary results obtained using this new approach.