A Lorentz-type mechanism for generation of small-scale irregularities in the heater-modified ionosphere

Abstract

We consider Lorentz-type mechanism for growth of LF small-scale turbulence due to generation of local field-aligned electric fields (FAEF) in the ionospheric F-region modified by powerful radio waves. The FAEF are induced by Lorentz-type forces caused by the large-scale pressure structure of the heated volume. We found that small- scale structuring of the large-scale depleted region (the patch) is a function of altitude and that the cross-field scale of small-scale irregularities is definitely determined by the gradient scale length in plasma density. This mechanism allows us to explain the generation of irregularities with scale lengths of 6 m or longer and observations of aftereffects within 30 seconds or longer after the pump switch-off if they are defined by the lifetime of the induced local sources. The predictions of the Lorentz-type mechanism are shown to be consistent with the measurements of the significant growth of DSEE typical times, related to relaxation of heater-induced small-scale irregularities, under conditions of strong natural turbulence observed as F-spread in the ionograms.