Ionospheric D region: VLF‐measured Electron Densities compared with Rocket‐Based FIRI‐2018 Model

Ground-based very low frequency (VLF) radio propagation in the Earth-ionosphere waveguide has enabled extensive electron number densities in the D region of the Earth’s ionosphere to be determined, by day typically below heights of 70-80 km and by night in the height range ∼75-90 km. Many rocket-based electron density measurements have also been reported in the literature from ∼60 km upwards using current probes, and radio propagation at a few MHz between the rocket and ground. Recently these rocket measurements have been summarized, and supplemented with D region production-loss modeling, giving rise to a near global model named FIRI-2018 (Faraday-International Reference Ionosphere) which provides electron number densities as functions of height, latitude (