(TH/P3-20) Momentum Transport and Ion Heating from Reconnection in the Reversed Field Pinch

V.A. Svidzinski1), F. Ebrahimi1), V. V. Mirnov1), S. C. Prager1)
1) University of Wisconsin-Madison, Madison, Wisconsin and the Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, United States of America

Abstract.  Tearing instabilities and reconnection events in fusion plasmas can have enormous impact on the macroscopic behavior of the plasma. This is true in tokamaks, and is especially true in reversed field pinch plasmas, in which multiple tearing instabilities can be present. Two particularly large effects are the sudden transport of toroidal angular momentum and ion heating that occurs during a sawtooth crash in RFP experiments. During the crash, the radial profile of the toroidal rotation flattens and the ion temperature doubles, both in a time period of about 100 microseconds. Neither effect can be explained by classical processes. We report here analytic and computational results on mechanisms that can cause these effects through the action of tearing instabilities. The key findings are: (1) a single tearing mode can transport momentum through the Maxwell stress (the mean Lorentz force arising from tearing fluctuations), and the effect is greatly enhanced from the nonlinear interactions that accompany multiple tearing modes; (2) viscous damping of tearing modes can contribute significantly to ion heating, even in a plasma with low collisionality, given the strongly sheared flows that accompany tearing.

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