Non-Linear Analysis of Mode Locking in MST
Abstract
A toroidally localized magnetic perturbation can form in the MST reverse field pinch just inside the reversal layer. Such perturbations have been shown to drift around the torus, following magnetic field lines in the direction of the ion diamagnetic drift velocity. We have determined that the mode trajectory follows the Sine-Gordon (SG) equation, i.e., it is a kink-type soliton. This represents the rotation angle around the minor axis that the mode makes in moving around the torus. The SG equation is obtained by summing the torques around the minor axis that are acting upon the island. Within the kink structure, local currents exist that can create a magnetic moment, which allows the kink to experience a potential well along the field lines proportional to grad B. When the center of the kink passes the poloidal gap, where the grad B force along the field lines is minimal, the radial magnetic field produced at the gap can change the force significantly, transforming the kink into a “breather” soliton and the mode locks.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2001
- Bibcode:
- 2001APS..DPPFP1015E