Parametric decay of plasma waves near the upper-hybrid resonance

An intense X wave propagating perpendicularly to dc magnetic field is unstable with respect to a parametric decay into an electron Bernstein wave and a lower-hybrid wave. A modified theory of this effect is proposed that extends to the high-intensity regime, where the instability rate $\gamma$ ceases to be a linear function of the incident-wave amplitude [1]. An explicit formula for $\gamma$ is derived and expressed in terms of cold-plasma parameters. Theory predictions are in reasonable agreement with the results of the particle-in-cell simulations reported in Ref.~[2].\\{[1]} I.~Y. Dodin and A.~V. Arefiev, Phys. Plasmas {\bf 24}, 032119 (2017).\\{[2]} A.~V. Arefiev, I.~Y. Dodin, A. K\"ohn, E.~J. Du Toit, E. Holzhauer, V.~F. Shevchenko, R.~G.~L. Vann, arXiv:1612.07860, to appear in Nucl. Fusion.