Author: Andrew J Cole
Requested Type: Pre-Selected Invited
Submitted: 2016-02-15 08:37:37
Co-authors: J.M. Finn, D.P. Brennan
500 W. 120th St., Mudd 206
New York, NY 10027
In this work it is shown that the error field penetration, or locking, behavior in plasmas having stable tearing modes with finite real frequencies in the plasma frame leads to unanticipated and important characteristics. In particular, we find that locking can drive a significant equilibrium flow, corresponding to the interaction with a backward propagating tearing mode in the plasma frame . This result is in stark contrast to previous locking theory, where the tearing layer locks to near zero flow velocity. (A result expected if the tearing layer were a rotating thin conductor, behaving as an AC induction motor.) Results are discussed for a few typical tearing mode regimes, including drift-tearing effects, and a new derivation showing that the inclusion of pressure gradient, curvature and parallel dynamics leads to finite real frequency viscous tearing modes.
Finally, we suggest an application of this effect: external magnetic fields with a spread in Fourier spectrum could be applied in order to drive finite plasma velocity locking at multiple tearing surfaces. Typically the phase velocities at the various rational surfaces will be different, and viscosity should lead to a smooth sheared rotation between these surfaces. Thus the main effect discussed in this work may lead to a method for maintaining flow shear, which is known to help stabilize modes and reduce transport.  J. Finn, A. Cole, and D. Brennan, "Error field penetration and locking to the backward propagating wave", Phys. Plasmas Letters, Vol. 22, 120701 (2015).