Abstract | The ionosphere is a dispersive medium for radiowave propagation, and as such is of critical importance for ground-space (GNSS) or ground-ground (High Frequency, HF) communication. Probing this environment using HF radars, such as SuperDARN, can provide information on local characteristics of the medium coupled with global characteristics resulting from the ray path-integration of the dispersion.
In order to extract the most of the information contained in radar observations, we want to simulate the propagation of HF radio waves in a realistic medium based on a first-principle ionosphere model developed at IRAP (TRANSCAR/IPIM family model). By comparing the simulated results of waves propagation with observed data from HF ionospheric radars of the SuperDARN chain, the main ionospheric parameters (e.g. density and temperature of electrons/ions) will be adjusted in the model through a recursive loop in order to fit as best as possible the observations. The goal is the development of a numerical tool that allows the reconstruction of the ionosphere over a wide spatial coverage with about one minute time resolution.
This method will help in return to better characterize the echoes of the HF SuperDARN radars or all other HF waves transmitters: since it will be possible to determine correctly the real path of the waves in the ionosphere and will allow assessing the distance from the radar and the altitude of the echoes and to know locally the real ionospheric refractive index, allowing to correct the radial velocities deduced from Doppler shift
The goal is the development of a numerical tool that allows reconstructing the ionosphere over a wide spatial coverage with about one minute time resolution. The first step has been to develop a new ray-tracing tool which will be ultimately coupled to IPIM. This code has been validated by checking error in propagation with respect to wave frequency, elevation angle, and density gradient with a simple synthetic symmetric ionosphere.
In parallel, we have been testing our code using realistic TRANSCAR simulation of the ionosphere in the Stokkseyri radar's field-of-view, and so far the ray tracing tool has given good consistency between the electron density variation and wave propagation. But more work is still needed to ensure physically accurate behavior of wave propagation in such disturbed ionosphere, in particular for strong density gradients.
In this poster, we will first introduce the ionosphere modeling and then the ray tracing tool itself. We shall discuss the current limitations of the code (e.g. spherical Earth), the numerical resolution of the propagation equations, the density gradients interpolation. |
