Nonlinear structuring of the ionosphere modified by powerful radio waves at low latitudes

Abstract

The problem of the nonlinear structuring of the modified ionosphere due to the self-focusing of the pump wave on the bunches of striations is investigated. Two main conditions of self-focusing are formulated: (1) propagation of the pump wave quite along the magnetic field for effective excitation of striations, and (2) trapping of the pump wave by large-scale irregularities. It is shown that both conditions can be easily satisfied for small inclination angles α of the magnetic field to the vertical. A detailed study of the low latitude case was performed using model calculations of the pump wave propagation. It is shown that at low latitudes self-focusing conditions also can be satisfied but mostly for the special form of the large-scale irregularities and mostly in the southern part of the pump wave beam. These results may reconcile apparent differences between radiowave and rocket probing of the irregularities.