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Title: Long-lifetime current-driven rotating kink modes in a non-line-tied plasma column with a free end
Authors: Intrator, T.P. ×
Furno, I
Ryutov, D.D.
Lapenta, Giovanni
Dorf, L
Sun, X #
Issue Date: 12-May-2007
Publisher: American Geophysical Union
Series Title: Journal of Geophysical Research vol:112 issue:A5
Conference: AGU Fall Meeting of the Division of Plasma Physics edition:48 location:Philadelphia, Pennsylvania date:October 30-November 3, 2006
Article number: A05S90
Abstract: We show the first experimental evidence for a magnetohydrodynamic kink instability in a current rope with one end that is free to move. This free end is partially insulated by sheath resistivity, so that the usual frozen in flux assumption for magnetohydrodynamics is violated in this region. The free end is therefore not line-tied to the axial boundary. We find the instability threshold is well below the classical Kruskal-Shafranov threshold, culminating in a long-lifetime saturated state. The presence of an axial flow further lowers the kink threshold and gives rise to a doppler-shifted frequency from rotation of the kink, where the eigenfunction is axially pushed in the flow direction. This lowered threshold may give rise to kink instabilities in situations with small magnetic twist that would otherwise be considered stable. Striking agreement with a theoretical analysis is demonstrated. The existence of a free end may be important for open flux tubes attached to the Sun, galactic jets associated with accretion discs, and spheromak startup.
ISSN: 0148-0227
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Plasma-astrophysics Section
× corresponding author
# (joint) last author

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