Wave-optical simulation of the oblique HF radio field



[1] A wave-optical simulation of the oblique HF radio field is carried out by means of the multiple phase screen (MPS) technique which is frequently used for study of atmospheric effects on the propagation of electromagnetic waves. Contrary to previous studies on ionospheric HF radio propagation, the simulation is carried out for a cone of HF radio waves transmitted with elevation angles 0-35° from a point source at the ground. The ionospheric phase screens are approximately orthogonal to the Earth's surface, and the curvature of the Earth is considered. The HF radio field is determined from the surface to the topside ionosphere in two dimensions (x,z) by using ionospheric phase path screens with a z-resolution of 10 m and a screen spacing of 0.5 km in x-direction. Reflection of radio waves at the Earth's surface is implemented for the MPS simulation by means of an artificial decrease of the refractive index at heights below the surface (surface acts like an ionospheric layer in this rough approximation). The results are checked by means of ray tracing. The wave-optical simulation is applied for description of focusing and defocusing of oblique HF radio waves around the main focus in the F1-region and along the caustics where radio scintillations of high spatial frequencies are found due to interference and diffraction effects. One example is presented for the impact of a sporadic E layer on the HF radio field. Angular spectra of received radio signals are calculated at different locations of the HF radio field.