fusion Theory & Computation

TORIC Full wave RF mode conversion

MHD and Stability

A majority of Magnetohydrodynamic (MHD) problems relevant to current fusion research, such as sawtooth oscillations, neoclassical tearing modes, magnetic reconnection in general, edge localized phenomena, and resistive wall modes, involve multifluid effects. These normally require a generalized Ohm's law, diamagnetism and collisionless (gyro)viscosity, and decoupling of ion and electron flows and temperatures. Consideration of self consistent equilibrium flows and realistic representations of the temperature anisotropies (or parallel viscosities) and the heat fluxes in low collisionality regimes are also necessary.

These effects are incorporated into a mainly fluid description of the plasma with what is referred to as extended MHD models. Our efforts in the PSFC theory group are aimed at developing and applying these more sophisticated descriptions to improve our models of tokamaks, other fusion devices, and space and astrophysical plasmas.

Examples of recent accomplishments:
* Collisionless closure issues resolved for MHD and drift orderings
* Unified theory of drift-resistive ballooning modes at edge of C-Mod
* Developed a 2-D Hall-MHD model of driven reconnection in X-point geometry

Representative current research topics:
* Long mean free path collisional closure for general distribution functions
* Neoclassical tearing mode studies with self-consistent extended MHD closures
* Drift-resistive ballooning theory with temperature gradients and sound waves

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