Integration of Kinetic Effects in Multi-Fluid Models of Reconnection: Towards Next-Generation Global Simulations

Abstract:

The inclusion of kinetic effects in multi-fluid descriptions of magnetic reconnection is a grand challenge for next-generation global simulation codes needed for space weather applications. We introduce a new model, which includes the full Maxwell equations and simultaneously, moments of the Vlasov equation for each species in the plasma. Electron inertia and pressure tensor effects are self-consistently included in the resulting equations without the need to include a generalized Ohm's law. Two limits of the new model are discussed: the 5-moment model which reduces to Hall MHD under the assumptions of vanishing electron inertia, infinite speed of light, and quasi-neutrality, and a 10-moment model with a Hammett-Perkins approximation for the heat flux. The results of the multi-fluid code are compared with those from fully kinetic particle-in-cell simulations for two reconnection challenge problems: the Harris sheet, and the coalescence of magnetic islands in large-scale systems. The latter brings out certain novel aspects of the importance of kinetic ion physics, not captured by earlier studies.

This research is supported by the NASA-NSF Partnership on Space Weather.