Ion-temperature-gradient-driven instability and anomalous ion heating in reversed-field pinches

A possible mechanism is suggested for direct ion heating in reversed-field pinches (RFP). The ion temperature gradient mode induces collisionless ion perpendicular viscosity which damps the velocity fluctuations associated with resistive magnetohydrodynamic (MHD) mode activity. It is found that the growth rate of the ηi instability is much larger than that in a tokamak, because the effects of both bad magnetic curvature and negative compressibility are enhanced in a RFP configuration. The anomalous perpendicular viscosity coefficient is estimated from the mixing length argument and the corresponding ion heating power due to viscous dissipation is found sufficient to balance the ion conductive losses