IFM

The IFM is a three‐dimensional, high‐resolution, multi‐ion model of the global ionosphere that is based on the USU Time‐Dependent Ionosphere Model (TDIM). The IFM has been continuously extended and improved over the years. The model covers the altitude range from 90 to 1600 km and all latitudes and longitudes. The spatial and temporal resolutions of the IFM are flexible. The finest spatial resolution for the present version is 2° in latitude and 5° in longitude and is variable in vertical direction (for example, 4 km for the E region and 20 km for the F region). The finest temporal resolution is 5 min. All these resolutions can be further increased upon the need of the model user. The IFM is based on a numerical solution of the continuity, momentum, and energy equations of multiple ion species. The equations are solved along magnetic field lines for individual convecting flux tubes of plasma, and the 3‐D nature of the model is obtained by following a large number of plasma flux tubes. The model takes account of field‐aligned diffusion, cross‐field electrodynamic drifts, thermospheric wind, neutral composition changes, energy‐dependent chemical reactions, ion production due to solar UV/EUV radiation and auroral precipitation, thermal conduction, diffusion‐thermal heat flow, and a myriad of local heating and cooling processes. The model also accounts for the displacement between the geomagnetic and geographic poles.

To run IFM, information on neutral composition, neutral wind, E × B drift field, solar UV/EUV radiation, and the precipitation and convection at high latitudes is needed.

The outputs of the IFM include 3‐D distributions of electrons and various ion species; electron and ion temperatures; TEC; and NmF2, HmF2, and other auxiliary ionospheric plasma parameters.