Peculiarities of leakage of the electromagnetic waves from striations

Abstract

It is well-known that an ordinary (O-mode) high frequency (HF) electromagnetic (EM) wave radiated into the ionosphere generates in the F-region upper-hybrid resonance (UHR) oscillations trapped in small-scale elongated plasma depletions (striations). Striations are not ideal resonators for UHR oscillations. There is some leakage of the HF energy from striations in the form of Z-mode waves. This result obtained in the quasi-electrostatic approximation is partly reconsidered in the present paper. It is shown in the 2D case that two EM waves (instead of one Z-mode) propagate from each side of a striation. The lowest eigenmodes of the electrostatic oscillations trapped in a striation excite at particular heights Z-mode waves that propagate significantly higher than the reflection height of the initial O-mode wave. This result exists for different angles of the O-mode radiation with respect to the vertical (both more and less than the critical angle).