Investigation of Electromagnetic-Flute-Mode Instability in a High-BetaZ-Pinch Plasma

Recent experiments (laser multiframe shadowgraphy and Faraday rotation diagnostics) with Al imploding wire arrays in the 1-MA "Zebra" accelerator at the Nevada Terawatt Facility have demonstrated that a significant amount of current is going through the central region of the high-beta precursor plasma. With time, the perturbations develop both long scale structures and short-wavelength oscillations in the directions perpendicular to the magnetic field. The most likely candidate for the observed phenomena is the flutelike electromagnetic modes. These are excited in the current-carrying high-beta inhomogeneous precursor plasma due to the curvature of the magnetic field produced by the current. These modes may also play a role in the stagnation phase of Z-pinches. In this paper, nonlinear equations describing electromagnetic-flute-type oscillations in the high-beta precursor plasma are derived, and the linear stage of instability of these waves is examined. A comparison with the experimental results is performed as well