Nonlinear harmonics coupled by parallel wave propagations in a time-dependent plasma flow

Abstract

In a time-dependent flow, nonlinear harmonics can be excited by coupling between linear waves and flow-induced harmonic waves. Examining the dispersion relations and selection rules for the coupling, we investigate nonlinearly coupled harmonics for waves propagating along the magnetic field line in a magnetized plasma as well as waves in an unmagnetized plasma. The coupled harmonics in a plasma flow are described by the analytic dispersion relations and selection rules. This nonlinear coupling is corroborated by the particle-in-cell simulation. The coupled-harmonics model describes a mechanism for excitation of nonlinear harmonics from linear waves in a time-dependent flow. The spectral analysis of the dispersion relation provides a useful way to evaluate the spatiotemporal behavior of a plasma flow.

Dispersion relation and instability for an anisotropic nonuniform flowing plasma

“…By analyzing the Vlasov equation, the effects of nonuniform flow and temperature on wave properties have been studied for a specific plasma flow, wave mode, and frequency regime [22][23][24][25]. On the other hand, a generalized dielectric tensor and a dispersion relation have been derived for plasmas with nonuniform densities, time-varying flows, and anisotropic temperatures [8,26]. In the kinetic analysis, an adequate distribution function should be adopted to satisfy the Vlasov equation.…”