FIRI-2018: MATLAB package for the lower ionosphere model

It is important to have information about the electron density in the lower ionosphere for predicting the energy parameters of very low frequency radio links. It can be provided by the Faraday International Reference Ionosphere model. We have implemented this model in the MATLAB programming software as a set of scripts, functions and data files. Since the wave method for predicting the electric field strength on the radio path is sensitive to low electron densities at low altitudes, the developed package implements exponential extrapolation of the electron density for altitudes below 55 km. The MATLAB source code is available at Github and MATLAB Central resources.