Past Event: Oden Institute Seminar

Mathematical modeling and AMR simulations on massively parallel architecture of astrophysical plasmas: application to partially ionized plasma under sun chromosphere conditions

Quentin Wargnier , Associated Researcher, CMAP, Ecole Polytechnique, Palaiseau, France

Abstract

This contribution deals with the fluid modeling of multicomponent magnetized plasmas in thermo-chemical non-equilibrium from the partially- to fully-ionized collisional regimes, aiming at simulating magnetic reconnection in Sun chromosphere conditions. Such fluid models are required for large-scale simulations by relying on high performance computing. The fluid model is derived from a kinetic theory approach, yielding a rigorous description of the dissipative and non-equilibrium effects and a well-identified mathematical structure. We start from a general system of equations that is obtained by means of a multiscale Chapman-Enskog method, based on a non-dimensional analysis accounting for the mass disparity between the electrons and heavy particles, including the influence of the electromagnetic field and transport properties. The latter are computed by using a spectral Galerkin method based on a converged Laguerre-Sonine polynomial approximation. Then, in the limit of small Debye length with respect to the characteristic scale in the solar chromosphere, we derive a two-temperature single-momentum multicomponent diffusion model coupled to Maxwell's equations, which is able to describe fully- and partially-ionized plasmas, valid for the whole range of solar chromosphere conditions. The second contribution is the development and verification of an accurate and robust numerical strategy based on a massively parallel code with adaptive mesh refinement capability. We rely on the canop code, based on two libraries: P4EST for the adaptive mesh refinement (AMR) capability and MUTATION++ for computing the transport properties with a high level of accuracy, in order to ensure that the full spectrum of scales and the dynamics of the magnetic reconnection process are captured. Finally, we present a 2D and 3D magnetic reconnection configuration in solar chromospheric conditions and assess the potential of the numerical strategy for simulating astrophysical plasmas. [[Work in collaboration with Marc Massot, Thierry Magin, Benjamin Graille and Nagi Mansour, as well as NASA SuperComputing Division of NASA Ames Research Center, and von Karman Institute, Belgium]]