Fine structure of high-altitude ionosphere during sub-storms

Dynamics of the fine structure of auroral ionospheric E-region is analyzed. The study was made during a sub-storm using data of frequency-spaced reception on a single-shock radio path layxng along the auroral zone. Observation period was in winter at night. Operating carriers were 10.7 and 16.7 MHz. The results obtained testify to the fact that parameters of the fine structure of auroral E-region are substantially dependent on the sub-storm phase. As the sub-storm is developing beginning with its preliminary phase dimensions of fine-scale inhomogeneities decrease, which is due to turbulent processes in a plasma. The decrease of dimensions of inhomogeneities is accompanied by the growth of relative fluctuations of electron concentration, angular spectra of scattered waves and with the decrease of the ionospheric opacity coefficient. All the above characteristics achieve maximum values at the active phase of sub-storm. After sub-storm the parameters of ionosphere recover (T=2.5-3hrs) up to the values corresponding to T=-(2.0-2.5hrs)