Fully Kinetic versus Reduced-kinetic Modeling of Collisionless Plasma Turbulence
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Grošelj_2017_ApJ_847_28.pdf
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Author(s)
Grošelj, Daniel
Cerri, Silvio S.
Navarro, Alejandro Bañón
Told, Daniel
Califano, Francesco
Jenko, Frank
Willmott, Christopher Edward
Loureiro, Nuno F.
Date Issued
September 2017
Journal
Astrophysical Journal
Publisher
American Astronomical Society
Citation
Grošelj, Daniel et al. “Fully Kinetic Versus Reduced-Kinetic Modeling of Collisionless Plasma Turbulence.” The Astrophysical Journal 847, 1 (September 2017): 28 © 2017 The American Astronomical Society
Version
Final published version
Abstract
We report the results of a direct comparison between different kinetic models of collisionless plasma turbulence in two spatial dimensions. The models considered include a first-principles fully kinetic (FK) description, two widely used reduced models (gyrokinetic (GK) and hybrid-kinetic (HK) with fluid electrons), and a novel reduced gyrokinetic approach (KREHM). Two different ion (beta[subscript i]) regimes are considered: 0.1 and 0.5. For (beta[subscript i]) = 0.5, good agreement between the GK and FK models is found at scales ranging from the ion to the electron gyroradius, thus providing firm evidence for a kinetic Alfvén cascade scenario. In the same range, the HK model produces shallower spectral slopes, presumably due to the lack of electron Landau damping. For (beta[subscript i]) = 0.1, a detailed analysis of spectral ratios reveals a slight disagreement between the GK and FK descriptions at kinetic scales, even though kinetic Alfvén fluctuations likely still play a significant role. The discrepancy can be traced back to scales above the ion gyroradius, where the FK and HK results seem to suggest the presence of fast magnetosonic and ion Bernstein modes in both plasma beta regimes, but with a more notable deviation from GK in the low-beta case. The identified practical limits and strengths of reduced-kinetic approximations, compared here against the FK model on a case-by-case basis, may provide valuable insight into the main kinetic effects at play in turbulent collisionless plasmas, such as the solar wind.
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
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DOI of Published Version
https://doi.org/10.3847/1538-4357/AA894D
