title: Formation and stability of impurity "snakes" in tokamak plasmas.
abstract: New observations of the formation and dynamics of long-lived impurity-induced helical "snake" modes in tokamak plasmas have recently been carried out on Alcator C-Mod. The snakes form as an asymmetry in the impurity ion density that undergoes a seamless transition from a small helically displaced density to a large crescent-shaped helical structure inside q<1, with a regularly sawtoothing core. The observations show that the conditions for the formation and persistence of a snake cannot be explained by plasma pressure alone. Instead, many features arise naturally from nonlinear interactions in a 3D MHD model that separately evolves the plasma density and temperature.
authors: PPPL, Princeton, New Jersey 08540, USA.
authors: L
authors: L
authors: Delgado-Aparicio
authors: L
authors: L
authors: Sugiyama
authors: R
authors: R
authors: Granetz
authors: D A
authors: DA
authors: Gates
authors: J E
authors: JE
authors: Rice
authors: M L
authors: ML
authors: Reinke
authors: M
authors: M
authors: Bitter
authors: E
authors: E
authors: Fredrickson
authors: C
authors: C
authors: Gao
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authors: M
authors: Greenwald
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authors: K
authors: Hill
authors: A
authors: A
authors: Hubbard
authors: J W
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authors: Hughes
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authors: Marmar
authors: N
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authors: Pablant
authors: Y
authors: Y
authors: Podpaly
authors: S
authors: S
authors: Scott
authors: R
authors: R
authors: Wilson
authors: S
authors: S
authors: Wolfe
authors: S
authors: S
authors: Wukitch