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Can you say something about the difference you experience between "plasma fluid dynamics" and "magnetohydrodynamics"? As I understand it, processes you can tre
by ncmncm 5y ago
Can you say something about the difference you experience between "plasma fluid dynamics" and "magnetohydrodynamics"?
As I understand it, processes you can treat as MHD practically never occur in nature, and are always something that has been carefully arranged by design so the system can be modeled at all. Astrophysicists seem to treat the two terms as interchangeable. Would you say that MHD suffices to model ion propulsion systems? To model anything, anywhere in nature?
- archermarks 5y agoMHD is a specific set of a assumptions you can make to reduce the plasma fluid equations to something more tractable. This includes things like assuming infinite conductivity and combining all of your species into a single "fluid". Those are reasonable assumptions for astrophysical plasmas but not at all for Hall thrusters, so we do not use MHD. In my work, we use the Euler equations for ions (assuming they lack viscosity), with electromagnetic and ionization source terms. Electrons are treated as massless and generally steady with respect to the ions. Both of their equations of motion can be derived starting with the Boltzmann equation and applying simplifying assumptions.