Towards Closures for Multi-Fluid Moment Simulations of Collisionless Plasmas

Abstract:

Fluid simulation remain an efficient and valuable tool to understand the global behavior of plasmas. However, as it well
known, fluid models require a closure approximation to yield a closed set of equations. Designing closures that capture correct
kinetic behavior in asymptotic regimes, specially in the presence of weak guide fields, remains a challenge. We present an
approach to developing such closures in the context of multi-fluid moment models. In these, each fluid is treated independently, with higher-order moments (pressure tensor, heat-flux tensor) evolved self-consistently with time-dependent equations. Electromagnetic fields are evolved with Maxwell equations, retaining displacement currents. The validity of these closures is determined by comparison with PIC simulations. A brief overview of the numerical schemes, implemented in the open-source computational framework Gkeyll, will also be presented.