A Multi-Fluid Multi-Species (MFMS) numerical code for simulating the solar atmosphere

Abstract:

The solar atmosphere is characterized by multiple periods and sizes involving a large spectrum of temporal and spatial scales. It is regulated through complex interactions between different species and chemical reactions, amongst other physical processes. Because of this complexity, an accurate description of all of these multi-scale phenomena in the solar atmosphere is out of the reach of standard single-fluid MHD models (Hartlep et al. 2012). Furthermore, the enrichment of low first ionization potential elements in the outer layer of the solar atmosphere (the FIP effect) is not fully described by the current theoretical models (e.g. Laming et al. 2017), since they employ semi-empirical static atmospheres.

In this framework, we develop a Multi-Fluid Multi-Species (MFMS) model in which aims to resolve the enigma of chemical fractionation and to address long-standing questions about chromospheric and coronal heating. The code, named Ebysus, is capable of treating species (e.g., hydrogen, helium, etc) and taking into account their excited and/or ionized level separately, including chemical reactions such as ionization/recombination, collisions, Ohmic diffusion, the Bierman battery, thermal conduction, and Hall effect. Additionally, inspired by the Bifrost code (Gudiksen et al. 2011), a robust and highly accurate numerical strategy coupled with modern computer architecture has been developed. This approach is able to cope with the large spectrum of scales and related numerical stiffness. In this presentation, we will provide further details about the numerical implementation, the integration of all the MFMS physical processes considered, and the tests used to validate the code. Preliminary but promising MFMS numerical simulations of Rayleigh-Taylor instabilities and magnetic reconnection in a two or three-dimensional configuration under solar atmosphere conditions have been performed.