Description of collisional frequencies for multifluid MHD models with Chapman-Cowling collision integrals
Abstract
We focus on the detailed description of the collisional frequency in the solar atmosphere based on a classical formalism with Chapman-Cowling collision integrals, as described by Zhdanov (2002) in the context of the 13N-moment model derived with a method of Grad (Grad 1949). These collision integrals allow linking the macroscopic transport fluxes of multifluid models to the kinetic scales involved in the Boltzmann equations. In this context, the collisional frequencies are computed accurately while being consistent at the kinetic level. We calculate the collisional frequencies based on this formalism and compare them with approaches commonly used in the literature in solar atmosphere conditions. To calculate the collisional frequencies, we focus on the collision integrals data provided by Bruno et al. (2010), which is based on a multicomponent hydrogen-helium mixture used in Jupiter atmosphere conditions. We propose a comparison with the classical formalism of Vranjes & Krstic (2013) and Leake & Linton (2013). We compare it with the formalism used in the three approaches and highlight the differences obtained in the distribution of the cross sections as functions of the temperature. Then, we quantify the disparities obtained in postprocessed simulations of a 2.5D solar atmosphere with the Bifrost code (see Gudiksen et al. 2011). Finally, we assess the impact of the collisional frequency in a simulated 2.5D solar atmosphere with a single-fluid radiative MHD model with ambipolar diffusion to consider ion-neutral interactions. Significant disparities in the cross sections have been obtained between these three formalisms. or instance, we note that Vranjes & Krstic 2013 did no integrate the transport cross sections. We will describe the impact of these discrepancies from previous results and the importance of doing these calculations properly.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMSH45B2362W