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Center for Nonlinear Studies |
The formulation of hybrid kinetic-MHD models for the dynamics of energetic particles in a MHD bulk tipically exploits powerful methods that lead to neglect fine-scale terms appearing in the fundamental equations of motion. While this modeling strategy has led to well consolidated plasma models, consistency issues may emerge in certain cases, especially concerning the energy balance. This may lead to the presence of spurious instabilities that are produced by nonphysical energy sources. The talk proposes alternative techniques based on the geometry of Hamiltonian mechanics and its variational principles. Partly inspired by Littlejohn's approach to guiding-center theory, the main idea is to apply physical approximations to the action principle (or the Hamiltonian structure) underlying the fundamental system, rather than operating directly on its equations of motion. Here, I will show how this method provides alternative energy-conserving variants of hybrid kinetic-MHD models, which suppress the spurious instabilities emerging in previous non-conservative schemes.
Host: Joshua Burby (T-5)