Dynamics of seed magnetic island formation due to geometrically coupled perturbations

Abstract

Seed magnetic island formation due to a dynamically growing external source in toroidal confinement devices is modeled as an initial value, forced reconnection problem. For an external source whose amplitude grows on a time scale quickly compared to the Sweet-Parker time of resistive magnetohydrodynamics, the induced reconnection is characterized by a current sheet and a reconnected flux amplitude that lags in time the source amplitude. This suggests that neoclassical tearing modes, whose excitation requires a seed magnetic island, are more difficult to cause in high Lundquist number plasmas.

Large experiment data analysis collaboration. Final progress report for period November 15, 1997 - November 14, 1998

“…Neoc lassical Tearin? Modes [1,2,[4][5][6][7][8][9]11,12,14,1%,15c,16,17,20a,2&,2Od,2Oe,21a,21b,22,241 Studies of neoclassical tearing modes have remained the dominant area of research on this grant. Our major role in their development was recognized through an invited paper at the 1998 Pittsburgh DPP-AB meeting 19,141 and through our inclusion as coauthors on some major TFI'R [2,4,8] and DIII-D 151 papers.…”

“…Also, linear and nonlinear theory and computation studies of classical tearing modes via the "almost ideal MHD" constraint has been the subject of a number of meeting presentations [17,21b] and has recently been published [ll]. Recent work has been concerned with developing a theoretical model [12,2Oa] for the magnitude of seed island perturbations due to, thereof. nor any of their employees, makes any warranty, express or implid, or assumes any kgal liability or responsibility for the accuracy, completeness, or usefulness of any information.…”