Generalized Fluid Models of the Braginskii Type

Hunana, P.; Passot, T.; Khomenko, E.; Martínez-Gómez, D.; Collados, M.; Tenerani, A.; Zank, G. P.; Maneva, Y.; Goldstein, M. L.; Webb, G. M.
Bibliographical reference

The Astrophysical Journal Supplement Series

Advertised on:
Number of authors
IAC number of authors
Refereed citations
Several generalizations of the well-known fluid model of Braginskii (1965) are considered. We use the Landau collisional operator and the moment method of Grad. We focus on the 21-moment model that is analogous to the Braginskii model, and we also consider a 22-moment model. Both models are formulated for general multispecies plasmas with arbitrary masses and temperatures, where all of the fluid moments are described by their evolution equations. The 21-moment model contains two "heat flux vectors" (third- and fifth-order moments) and two "viscosity tensors" (second- and fourth-order moments). The Braginskii model is then obtained as a particular case of a one ion-electron plasma with similar temperatures, with decoupled heat fluxes and viscosity tensors expressed in a quasistatic approximation. We provide all of the numerical values of the Braginskii model in a fully analytic form (together with the fourth- and fifth-order moments). For multispecies plasmas, the model makes the calculation of the transport coefficients straightforward. Formulation in fluid moments (instead of Hermite moments) is also suitable for implementation into existing numerical codes. It is emphasized that it is the quasistatic approximation that makes some Braginskii coefficients divergent in a weakly collisional regime. Importantly, we show that the heat fluxes and viscosity tensors are coupled even in the linear approximation, and that the fully contracted (scalar) perturbations of the fourth-order moment, which are accounted for in the 22-moment model, modify the energy exchange rates. We also provide several appendices, which can be useful as a guide for deriving the Braginskii model with the moment method of Grad.
Related projects
Solar Eruption
Numerical Simulation of Astrophysical Processes

The general aim of this project is the investigation of astrophysical processes through the use of state­of­the­art numerical codes on massively parallel computers. More specifically, the research in many astrophysical fields requires an understanding of gas dynamical, magnetic, radiative transfer and gravitational phenomena not accessible to

Project Image
Solar and Stellar Magnetism

Magnetic fields are at the base of star formation and stellar structure and evolution. When stars are born, magnetic fields brake the rotation during the collapse of the mollecular cloud. In the end of the life of a star, magnetic fields can play a key role in the form of the strong winds that lead to the last stages of stellar evolution. During

Felipe García