Parametric excitation of Bernstein modes in laser-produced plasma

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Abstract
Parametric excitation of electron Bernstein modes in magnetized laser-produced plasma is studied. A dispersion relation is derived for the pump and scattered light wave vectors collinear and perpendicular to a uniform magnetic field in a uniform plasma and numerical solutions are obtained for the growth rate in collisionless plasma. These are then compared to an improved analytic approximation for the growth rate, and excellent agreement is obtained. Magnetic fields considered range from 10 to 1000 kG. Threshold pump intensities are estimated by including collisions or density inhomogeneity of the plasma. Ion-sound wave excitation (stimulated Brillouin scattering) is also seen and compared with the Bernstein mode results. In some regimes, the two thresholds are quite comparable. The numerical code also yields a nearly purely growing mode near the critical density. Numerical results are in good agreement with an analytic approximation, for this close cousin of the oscillating two stream instability.