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On the effect of resistive diffusion on line-tied kink modes in cylindrical geometry

Author: Gian Luca Delzanno
Requested Type: [none selected]
Submitted: 2006-12-07 17:46:15

Co-authors: E. G. Evstatiev, J. M. Finn

Contact Info:
Los Alamos National Laboratory
PO Box: 1663
Los Alamos, NM   87545

Abstract Text:
In a recent paper [1], Evstatiev et al. proposed a new method to analyze the linear stability of line-tied kink modes in cylindrical geometry. The method consists of summing up a number of one-dimensional (radial) eigenfunctions to obtain the full two-dimensional solution of the problem and has been successfully applied to both ideal and resistive MHD [1].
The present work investigates the role of resistivity on line-tied kink modes [2] because of the importance of resistivity in laboratory experiments [3,4] and in simulations. Resistivity affects the problem in two ways. First, it disallows perfect line-tying at the two end-plates of the cylinder. Second, some of the radial eigenfunctions used to construct the full solution of the problem can be unstable tearing modes instead of stable ideal modes, thus opening the possibility of tearing-like instabilities in line-tied configurations. In order to address these two issues, we will use our new method to study different equilibria where the field line pitch as a function of radius can be monotonically increasing (tokamak-like), monotonically decreasing (RFP-like) or constant. We will show the existence of slowly growing resistive modes below the threshold for ideal stability. These modes grow at a rate proportional to resistivity and we do not observe tearing-like scaling or the presence of current sheets.
[1] E. G. Evstatiev, G. L. Delzanno, J. M. Finn, Physics of Plasmas 13, 072902 (2006).
[2] G. L. Delzanno, E. G. Evstatiev, J. M. Finn, 'The role of resistivity on line-tied kink modes in cylindrical geometry', submitted.
[3] W. F. Bergerson, C. B. Forest, G. Fiksel, D. A. Hannum, R. Kendrick, J. S. Sarff, S. Stambler, Phys. Rev. Lett. 96, 015004 (2006).
[4] I. Furno, T. P. Intrator, D. D. Ryutov, S. Abbate, T. Madziwa-Nussinov, A. Light, L. Dorf, G. Lapenta, Phys. Rev. Lett. 97, 015002 (2006).

Characterization: E6


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