**Topic/Type**:
2.1 MHD, EHD & other fluid methods, Poster

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Singularly Perturbed ODE Models in Viscous Magnetohydrodynamics

**
Wieslaw Marszalek
**

*
DeVry University, North Brunswick, NJ, USA*

We consider singularly perturbed resistive-viscous MHD equations of the form , , where stands for derivative with respect to , is the wave speed, and is a parameter. Such systems of singularly perturbed MHD equations include the MHD models of intermediate shocks [1], when the resistivity and viscosity and/or are present and one of the viscosity parameters plays the role of "small" . The , two components of the magnetic induction vector () and is the velocity. When we obtain a system of differential-algebraic equations [2] (or DAEs) rather than singularly perturbed ODEs. The former have singularities which typically behave as impasse points, singular pseudo nodes, saddles, foci points, or singularity induced bifurcation (SIB) points [3]. The pseudo equilibrium and SIB points allow for smooth transitions between the plus (supersonic) and minus (subsonic) Riemann sheets with either one or two analytic trajectories crossing the singularity (sonic) curve and other trajectories of lower smoothness.

In the paper we analyze the singularly perturbed MHD equations with "small" and examine their qualitative properties for various sets of resistivity and viscosity coefficients and .

[1] C. C. Wu, "Formation, structure, and stability of MHD intermediate

shocks", J. Geophys. Research, vol.95, no.A6, 1990, pp.8149-8175.

[2] W. Marszalek, "Fold points and singularities in Hall MHD differential-algebraic equations", IEEE Trans. on Plasma Sci., vol.37, no.1, 2009, pp.254-260.

[3] R. Beardmore, "The singularity-induced bifurcation and its Kronecker normal form", SIAM J. Matrix Analysis, vol.28, no.1, 2001, pp.126-137.