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A solvable self-similar model of the sausage instability in a resistive Z pinch

Journal Article · · Physics of Fluids B; (USA)
DOI:https://doi.org/10.1063/1.859723· OSTI ID:5569948
 [1]
  1. Beam Physics Branch, Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375-5000 (US)

A solvable model is developed for the linearized sausage mode within the context of resistive magnetohydrodynamics. The model is based on the assumption that the {ital fluid} {ital motion} of the plasma is self-similar, as well as several assumptions pertinent to the limit of wavelength long compared to the pinch radius. The perturbations to the magnetic field are {ital not} assumed to be self-similar, but rather are calculated. Effects arising from time dependences of the {ital z}-independent perturbed state, e.g., current rising as {ital t}{sup {alpha}}, Ohmic heating, and time variation of the pinch radius, are included in the analysis. The formalism appears to provide a good representation of global'' modes that involve coherent sausage distortion of the entire cross section of the pinch, but excludes modes that are localized radially, and higher radial eigenmodes. For this and other reasons, it is expected that the model underestimates the maximum instability growth rates, but is reasonable for global sausage modes. The net effect of resistivity and time variation of the unperturbed state is to decrease the growth rate if {alpha}{approx lt}1, but never by more than a factor of about 2. The effect is to increase the growth rate if {alpha}{approx gt}1.

OSTI ID:
5569948
Journal Information:
Physics of Fluids B; (USA), Journal Name: Physics of Fluids B; (USA) Vol. 3:7; ISSN 0899-8221; ISSN PFBPE
Country of Publication:
United States
Language:
English