Integrating extended MHD and kinetic physics into the next-generation OpenGGCM

Abstract:

Going beyond one-fluid MHD is crucial to properly model the ion- and electron-scale reconnection physics in collisionless plasmas, as present in Earth's geospace environment.

This presentation introduces the next-generation OpenGGCM, based on J.~Raeder's well-known global magnetospheric model. OpenGGCM has been modularized using the libMRC framework, so that components can easily be exchanged. For example, the MHD solver can be replaced by using a coupled version of the multi-fluid moment code Gkeyll, that handles multiple species and integrates kinetic effects, e.g., a full pressure tensor. We have also added the option to couple OpenGGCM to the widely used ATHENA code. Similarly, there are options for inner magnetosphere and ionosphere models.

Mesh refinement is available in the new version, enabling the use of a computational grid that puts very high resolution at the reconnection current sheets at the dayside magnetopause and in the magnetotail while saving computational effort using a coarser resolution in regions that have no small-scale dynamics. Mesh refinement is implemented as a number of sparse-matrix multiplications to fill ghost cells, and to correct fluxes and electric fields. It supports exact flux conservation for the cell-centered fluid quantities and the staggered Yee grid for the electromagnetic fields, maintaining the magnetic field divergence-free to machine precision.

We will present computational tests and show applications of the next-generation OpenGGCM to simulations of reconnection at Ganymede and at Earth's dayside magnetopause.