Wave‐optical simulation of the oblique HF radio field

Abstract

[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 0-35Њ 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 F 1 -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.

lensing from small-scale travelling ionospheric disturbances observed using lofar

“…The use of numerical phase screen models in the ionosphere has previously focused on anthropogenic radio sources, such as ground-or space-based radar systems and GNSS signals (e.g. Carrano et al, 2020;Ding et al, 2021;Hocke and Igarashi, 2003;Ludwig-Barbosa et al, 2019;Wang et al, 2014), meaning that care must be taken in defining the input spectrum of a natural source as considered here. As the source is incoherent, each angular component must be treated separately, to avoid the spurious phase relationships between the components that occur if they are combined into a single spectrum.…”

HF propagation results from the Metal Oxide Space Cloud (MOSC) experiment

“…Figure (top) shows such a simulated sphere, while Figure (bottom) displays the relative signal strength for an 8 MHz plane wave traveling from left to right in the figure. The propagation results, derived from a wave‐optics calculation [ Hocke and Igarashi , ], show clearly how the power diverges as the wave propagates through the sphere. In this scenario it is plausible that the power from waves below 8 MHz was refracted off axis passing through the samarium cloud and was not received along the great circle path at Wotho; signals at higher frequencies would suffer less refraction and could thus reach Wotho.…”

“…Since Haselgrove [1955] set down the differential equations governing raypaths in an anisotropic medium for numerical integration techniques [Haselgrove, 1955], the equations have been used extensively [Jones and Stephenson, 1975;Coleman, 1993;Zawdie et al, 2016] to study the propagation of HF energy through the ionosphere. In our work to model the HF sounder observations, we have used PHaRLAP, a HF radio wave ray tracing MATLAB toolbox developed by Dr. Manuel Cervera, that contains a variety of ray tracing engines of various sophistications from 2-D ray tracing to full 3-D magnetoionic ray tracing [Cervera and Harris, 2014].…”

Observations of High Definition Symmetric Quasi‐Periodic Scintillations in the Mid‐Latitude Ionosphere With LOFAR

“…The pattern of phase variations can take many forms, such as a sinusoidal wave. Approximating the ionosphere in this way (or as several discrete screens) has been widely used for modeling ionospheric radio propagation (e.g., Briggs & Parkin, 1963;Carrano et al, 2020;Hocke & Igarashi, 2003;Meyer-Vernet, 1980). A schematic, reproduced from Boyde et al (2022) showing the basis of the phase screen model used here is shown in Figure A1 in the Appendix.…”