A Ray Tracing Simulation of HF Ionospheric Radar Performance at African Equatorial Latitudes

Abstract

High‐frequency (HF) coherent radars are widely applied for studying electrodynamic processes in the Earth's upper atmosphere and ionosphere. Super Dual Auroral Radar Network (SuperDARN) is an international network of such radars located at high‐ and middle‐latitude regions in the Northern and Southern Hemispheres. A major criterion of the HF coherent radar technique entails that the HF waves propagate orthogonal to the geomagnetic field lines (aspect angle ≤1°) in the ionospheric irregularity region from where backscatter originates. In this paper we present an HF ray tracing simulation of the performance of three proposed equatorial HF radar systems for the African equatorial sector. We use a number of realistic average ionospheres deduced from the International Reference Ionosphere (IRI) 2012 model and magnetic field geometries from the International Geomagnetic Reference Field (IGRF) to determine likely propagation paths and orthogonality conditions for such radar systems. The east‐west azimuth ( ∼25° range) has a significant likelihood of achieving a SuperDARN‐type backscatter in the African equatorial sector, mainly due to the prevailing magnetic field geometry. This analysis provides a feasibility study for developing a SuperDARN‐like radar for studying the equatorial ionosphere over the African longitude sector, for example, in determining the technical radar characteristics such as preferable operating frequencies, antenna boresight orientation, and azimuth coverage and provides a simulation of the expected localization of radar backscatter as a function of radar location and beam direction, as well as the time of day, season, and sunspot number.

Development of Low Latitude Long Range Ionospheric Radar for Observing Plasma Bubble Irregularities and Preliminary Results

“…At low latitudes, the background ionosphere and geomagnetic field are significantly different from those at high latitude and polar region. A ray tracing simulation is useful to determine Journal of Geophysical Research: Space Physics 10.1029/2023JA032099 HF radar operating parameters (e.g., Li et al, 2021;Michael et al, 2020;Nishitani & Ogawa, 2005). For example, ray tracing simulations were performed before the development of Hokkaido SuperDARN radar (Nishitani & Ogawa, 2005), as well as for the potential equatorial HF radar in Africa (Michael et al, 2020).…”

“…A ray tracing simulation is useful to determine Journal of Geophysical Research: Space Physics 10.1029/2023JA032099 HF radar operating parameters (e.g., Li et al, 2021;Michael et al, 2020;Nishitani & Ogawa, 2005). For example, ray tracing simulations were performed before the development of Hokkaido SuperDARN radar (Nishitani & Ogawa, 2005), as well as for the potential equatorial HF radar in Africa (Michael et al, 2020). Before designing the LARID system, a ray tracing simulation was performed to evaluate the key working parameters of the system, including operational frequency, beam direction, possible positions of irregularity backscatter echoes.…”

“…When a radar beam points toward the east or west direction, the condition that the radar beam is perpendicular to magnetic field can be satisfied. The ray tracing simulations of the possibility of HF radar backscatter echoes at equatorial latitudes in the African sector (Michael et al., 2020) and low latitudes in the East and Southeast Asian sector (Li et al., 2021) showed that the perpendicular conditions could be achieved in the east or west looking beams. In recent years, SuperDARN‐like HF radars were proposed to be built at equatorial and low latitudes, for example, in Africa (Lawal et al., 2018; Michael et al., 2020) and in Asia (Li et al., 2021).…”

Modeling and Validating a SuperDARN Radar's Poynting Flux Profile

“…Historically, SuperDARN‐related modeling efforts have focused on HF ray paths and determining where the rays satisfy the aspect angle condition (e.g., André, et al., 1997; Michael et al., 2020). One advantage of this technique is that it does not require one to simulate plasma density irregularities – it is assumed that irregularities are present everywhere.…”

Quasi‐Optical Ray Tracing of Gaussian Beams in the Magnetosphere

“…The modern application of tracing rays through the ionosphere using computer modeling, pioneered by Haselgrove (1955Haselgrove ( , 1957, has grown over the years with many codes written to suit specific purposes. Examples include the Stanford very low frequency (VLF) 3-D ray tracing software package (Golden et al, 2010), HOTRAY (Horne, 1989), MOJO (Zawdie et al, 2016), and the high frequency ray tracing simulation for the Super Dual Auroral Radar Network (SuperDARN) (Coleman, 1998;Michael et al, 2020). Ray tracing codes have become increasingly more complex going from relatively simple 2-D tracing in the ionosphere to 3-D tracing out into the plasmasphere and incorporating more options such as a density and magnetic field model choices.…”