202 research outputs found
Limitations of Hall MHD as a model for turbulence in weakly collisional plasmas
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
Alfven 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.Comment: Accepted for publication in Nonlinear Processes in Geophysics, 15
pages, 10 figure
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