Instability of modified Zakharov-Kuznetsov solitons in an inhomogeneous partially degenerate electron-ion magnetoplasma.

Abstract

Linear and nonlinear propagation characteristics of multidimensional drift ion-acoustic (IA) solitons are studied in an inhomogeneous partially degenerate electron-ion magnetoplasma. A modified Zakharov-Kuznetsov (mZK) equationis deduced, accounting for the longitudinal as well as the transverse dispersions. It is shown that the mZK equationadmits a distinct solution, revealing excitation of a pulse-shaped soliton when the phase speed exceeds by the wave dispersion. For the instability condition of the waves, a novel growth rate (γ) is derived by modifying the standard small-k expansion scheme. The instability criterion, given for long-wavelength IA waves, has not been described elsewhere. Numerical analysis show that solitary pulses gain energy from the ion drift, involving into instability: it saturates with amplification of the unstable potentials. Similarly trapped electrons lead to unstable growth of the solitary waves by enhancing γ. This study is relevant to compact stars and to high-density facilities where density inhomogeneity ensues the unstable drift modes. The instability analysis is important in understanding anomalous diffusion, which reduces the lifespan (τ=γ^{-1}) of magnetically confined plasma.