Title: Kinetic Landau-fluid closures of non-Maxwellian distributions

Abstract

New kinetic Landau-fluid closures, based on the cutoff Maxwellian distribution, are derived. A special static case is considered (the frequency ω=0). In the strongly collisional regime, our model reduces to Braginskii's heat flux model, and the transport is local. In the weak collisional regime, our model indicates that the heat flux is non-local and recovers the Hammett–Perkins model while the value of the cutoff velocity approaches to infinity. We compare the thermal transport coefficient χ of Maxwellian, cutoff Maxwellian and super-Gaussian distribution. The results show that the reduction of the high-speed tail particles leads to the corresponding reduction of the thermal transport coefficient χ across the entire range of collisionality, more reduction of the free streaming transport toward the weak collisional regime. In the collisionless limit, χ approaches to zero for the cutoff Maxwellian and the super-Gaussian distribution but remains finite for Maxwellian distribution. χ is complex if the cutoff Maxwellian distribution is asymmetric. The Im(χ) approaches to different convergent values in both collisionless and strongly collisional limit, respectively. It yields an additional streaming heat flux in comparison with the symmetric cutoff Maxwellian distribution. Furthermore, due to the asymmetric distribution, there is a background heat flux q0 though there ismore » no perturbation. Furthermore, the derived Landau-fluid closures are general for fluid moment models, and applicable for the cutoff Maxwellian distribution in an open magnetic field line region, such as the scape-off-layer of Tokamak plasmas, in the thermal quench plasmas during a tokamak disruption, and the super-Gaussian electron distribution function due to inverse bremsstrahlung heating in laser-plasma studies.« less

Authors:

Fan, Kaixuan  ^[1];

• Search DOE PAGES for author "Fan, Kaixuan"
• Search DOE PAGES for ORCID "0000-0002-2751-8809"

Xu, Xueqiao  ^[2];

• Search DOE PAGES for author "Xu, Xueqiao"
• Search DOE PAGES for ORCID "0000-0003-1838-9790"

Zhu, Ben  ^[2];

• Search DOE PAGES for author "Zhu, Ben"
• Search DOE PAGES for ORCID "0000-0003-2225-045X"

Li, Pengfei  ^[1]

• Search DOE PAGES for author "Li, Pengfei"
• Search DOE PAGES for ORCID "0000-0001-6655-723X"

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+ Show Author Affiliations

1. Peking Univ., Beijing (China)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:

Wed Apr 20 00:00:00 EDT 2022

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); National Key Research and Development Program of China

OSTI Identifier:

1877969

Alternate Identifier(s):

OSTI ID: 1864071

Report Number(s):

LLNL-JRNL-830507
Journal ID: ISSN 1070-664X; 1046838; TRN: US2307446

Grant/Contract Number:  

AC52-07NA27344; 2017YFE0301100; 2017YFE0301101; LLNL-JRNL-830507

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 29; Journal Issue: 4; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Fluid dynamics; Kinetic theory; Thermal transport; Thermal diffusivity; Plasmas; Laser-induced plasma; Tokamaks; Particle distribution functions; Transport properties