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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 2
Nonlin. Processes Geophys., 16, 219–232, 2009
https://doi.org/10.5194/npg-16-219-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Coupling between large and small scale turbulence in space...

Nonlin. Processes Geophys., 16, 219–232, 2009
https://doi.org/10.5194/npg-16-219-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  27 Mar 2009

27 Mar 2009

Limitations of Hall MHD as a model for turbulence in weakly collisional plasmas

G. G. Howes G. G. Howes
  • 505 Van Allen Hall, Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA

Abstract. The limitations of Hall MHD as a model for turbulence in weakly collisional plasmas are explored using quantitative comparisons to Vlasov-Maxwell kinetic theory over a wide range of parameter space. The validity of Hall MHD in the cold ion limit is shown, but spurious undamped wave modes exist in Hall MHD when the ion temperature is finite. It is argued that turbulence in the dissipation range of the solar wind must be one, or a mixture, of three electromagnetic wave modes: the parallel whistler, oblique whistler, or kinetic Alfvén waves. These modes are generally well described by Hall MHD. Determining the applicability of linear kinetic damping rates in turbulent plasmas requires a suite of fluid and kinetic nonlinear numerical simulations. Contrasting fluid and kinetic simulations will also shed light on whether the presence of spurious wave modes alters the nonlinear couplings inherent in turbulence and will illuminate the turbulent dynamics and energy transfer in the regime of the characteristic ion kinetic scales.

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