Singularities of ionization-field instability and structurization of plasma of high-pressure non-self-maintained free-localized discharge in the field of a quasi-monochromatic microwave

A self-consistent set of the equations for the electromagnetic field and balance of plasma concentration in view of ambipolar diffusion and the equation for the fast oscillating component of electron motion in a variable field are used to investigate the linear stage of ionization-field instability of the plasma of high-pressure non-self-maintained discharge in the approximation of unbounded plasma in a plane quasi-monochromatic microwave packet. Green‘s function is constructed. In the simplest one-dimensional formulation of the problem, assuming that all parameters of the plasma and field vary only in the direction of propagation of the wave packet, the saddle point approximation is used to derive the dominant terms of asymptotic expansion of Green's function in two limiting cases; namely, for $t\to\infty$, $\vert z-z_0\vert\to0$, and for $t\ge0$, $\vert z-z_0\vert\to\infty$. It is demonstrated that, contrary to the existing notion of insignificant importance of ionization-field instability in a high-pressure plasma, this instability may produce a high rate of development of perturbations in such a plasma and have a decisive effect on the structure of plasma inhomogeneity being formed. A method is suggested of stabilizing ionization-field instability of a microwave plasma by selecting a proper shape of the wave packet, including an increase in the effective width of the frequency band emitted by the source.