Evolution of a stratified plasma structure induced by local heating of the ionosphere

A three-dimensional non-stationary problem of striated plasma density structure formation and relaxation during and after thermal heating of the F-layer of the ionosphere by powerful radio waves is investigated both numerically and analytically. A theoretical analysis is carried out, taking account of quasi-regular gradients of the concentration of the background plasma, ambient geophysical factors, as well as the altitudinal dependence of transport coefficients of electrons and ions in plasma. The results of the calculations are compared with experimental data obtained from measurements of the reflection parameters of radio waves scattered from plasma irregularities in the ionosphere artificially induced by heating for vertical and oblique incidence of HF-waves. The possibility of generating a quasi-periodical structure in the disturbed plasma region during local heating of the ionosphere is examined both theoretically and experimentally. Using a quasi-homogeneous model of the ionosphere, a more realistic relaxation time dependence upon the transverse scales of plasma disturbances close to the experimental data is obtained and examined for a varying degree of anisotropy of each inhomogeneity in the plasma grating structure.