Regions of Validity for the 10-Moment, Two Fluid Plasma Model

Abstract

Two plasma models under consideration are the 5-moment, two-fluid and the 10-moment, two-fluid models. The 10-moment, two-fluid plasma model offers the ability to capture nonisotropic effects. The model is derived by taking the first three moments of the Boltzmann equation, taking care to account for the collisions. This yields the scalar continuity equation, the momentum vector equation, and the anisotropic pressure tensor for the ion and electron fluids. The 5-moment model assumes isotropy, and therefore only employs a scalar pressure. Accordingly, with the use of an equation of state, the 5-moment, two-fluid system has a scalar energy equation instead of the pressure tensor. Dispersion diagrams illustrate that including the collision term is necessary for the 10-moment model to recover the isotropic case. Two-fluid effects are captured by the momentum equations, while the anisotropic pressure tensor captures the neutral shear and finite Larmor radius effects. The objective of the research is to compare the two-plasma fluid models using the WARPX code developed at the University of Washington. The 10-moment, two-fluid plasma model is numerically implemented via an approximate Reimann solver employing the finite volume method. Investigations of self-consistent, non-linear simulations starting from equilibria in different regimes are then conducted. The 5-moment, two-fluid and the 10-moment, two-fluid models are computationally investigated. Including the collision term in the anisotropic pressure tensor equation is necessary to capture the lower hybrid drift instability (LHDI) phenomenon.