Changes of the electron concentration profile during local heating of the ionospheric plasma

Using numerical simulation of a non-stationary problem of thermodiffusion and diffusive spreading of the electron component of the dense cold ionospheric plasma, the processes of formation and relaxation of strong disturbances of the electron temperature and concentration in the E- and F-regions of the middle-latitude ionosphere are examined, taking into account the altitudinal distribution of the electron transport coefficients. The cases of local heating and heating at separated altitudes of the ionospheric plasma by powerful radio waves generated from ground-based HF-facilities are numerically investigated. The numerical simulations of the non-stationary problem are compared with the analytical evaluations carried out for the stationary and quasi-stationary heating models. Results obtained from numerical experiments give good explanations of the experimentally observed deformation of the altitudinal ionospheric plasma density profile and the creation of negative cavities in the upper ionosphere and positive cavities in the lower ionosphere during the process of plasma heating.