Sherwood 2015

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approvedsherwood15_abstract_wlhuang.pdf2015-01-18 00:29:02Wenlong Huang

Theory of mode locking and island suppression by resonant magnetic perturbations in Rutherford regime

Author: Wenlong Huang
Requested Type: Consider for Invited
Submitted: 2015-01-18 00:18:51

Co-authors: Ping Zhu

Contact Info:
University of Science and Technology of China
96 Jinzhai Road
Hefei, Anhui   230026

Abstract Text:
We demonstrate in theory that the recently observed tearing mode locking and magnetic island suppression by resonant magnetic perturbations (RMPs) in J-TEXT experiments correspond to different states of a same dynamic system that is governed by the torque balance and the nonlinear island evolution equations in the Rutherford regime. In particular, the locked mode is the exact steady state of this system. A new analytical solution has been obtained for such a steady state, which quantifies the dependence of the locked island width on RMP amplitude and yields the RMP threshold for mode locking in different plasma regimes. Furthermore, two different branches of mode locking have been revealed by the new analytical solution and the branch with suppressed island size turns out to be unstable in general. On the other hand, when the RMP amplitude is below the mode locking threshold, our theory analysis indicates that the system admits time-averaged steady states of island suppression along with transient oscillations of the island width and rotational frequency, achieved through the RMP modulation of the tearing mode rotational frequency in absence of mode locking.


March 16-18, 2015
The Courant Institute, New York University