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Paper: Numerical Modeling of Weakly Ionized Plasmas
Volume: 359, Numerical Modeling of Space Plasma Flows: Astronum-2006
Page: 178
Authors: O'Sullivan, S.; Downes, T.P.
Abstract: Numerical investigations of astrophysical plasma flows often rely on the ideal magnetohydrodynamic (MHD) approximation. In the case of weakly ionized plasmas the most questionable assumption of this is that the gas may be adequately approximated as a perfectly conducting single fluid. In direct consequence, the field lines are frozen into the bulk flow and may exert unrealistic forces on the gas in situations where magnetic diffusion should be important. A more appropriate treatment under these conditions is to discard the flux-freezing approximation by allowing charged species (i.e. electrons, ions, charge carrying dust grains) to have relative motions and compete in their interactions with the neutral gas component and the magnetic field. Taking such a multifluid approach admits ambipolar and Hall diffusion effects which can have a significant influence on the dynamics of the plasma.

Conventional explicit numerical schemes have been shown to have a vanishing stable time step limit as the Hall effect becomes large and implicit schemes are, by nature, difficult to implement on distributed architectures, particularly when adaptive mesh refinement (AMR) is used. We present a novel explicit numerical scheme which allows a very significant claw-back of the deficit in ef- ficiency when compared with implicit techniques. In addition, given that the scheme is explicit, it is straightforward to plug into existing AMR packages.

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