Pressure-gradient-driven tokamak ''resistive magnetohydrodynamic'' instability in the banana-plateau collisionality regime

The moment equation approach to neoclassical processes is used to derive the linearized electrostatic perturbed flows, currents, and resistive MHD-like equations for a tokamak plasma. The new features of the resultant ''neoclassical magnetohydrodynamics,'' which requires a multiple length scale analysis for the parallel eigenfunction, but is valid in the experimentally relevant banana-plateau regime of collisionality, are: (1) a global Ohm's law that includes a fluctuating bootstrap current resulting from the ''parallel'' electron viscous damping (at rate μ/sub e/) of the poloidal flow due to the perturbed radial pressure gradient; (2) reduction of the curvature effects to their flux surface average because Pfirsch--Schlueter currents cancel out the lowest-order geodesic curvature effects: (3) an increased polarization drift contribution with B-2, replaced by B-2/sub Theta/ where B/sub Theta/ is the poloidal magnetic field component. An electrostatic eigenmode equation is determined from delxJ = 0. For the unstable fluid-like eigenmodes, the new viscous damping effects dominate (by epsilon-3/sup //2) over the curvature effects, but the growth rates still scale roughly like resistive-g or resistive-ballooning modes, γ/sub μ/tau/sub A/approx.n/sup 2/3/S/sup 1/3//sub N/β/sup 2/3//sub T/ x ( μ/sub e//ν/sub e/)/sup 1/3/. Diamagnetic drift frequency corrections to these new modes are also discussed