Title: A New Empirical Model for Ionospheric Total Electron Content

Abstract: We present a new high resolution empirical model for the ionospheric total electron content (TEC) that includes dependency of TEC on solar flux, season, and geomagnetic activity. TEC data are obtained from the global navigation satellite system (GNSS) receivers with 1° x 1° spatial resolution and 5 minute temporal resolution. The application of several parameters describing solar and geomagnetic activity is evaluated. Variability in solar activity is described by use of the extreme ultraviolet flux (EUV) rather than the often used 10.7cm solar radio flux (f10.7) in order to capture the solar spectrum more comprehensively. We also include time delays for this parameter on the order of several days as well as seasonal modulation of the solar output. To reflect the influence of geomagnetic activity, the Ap3 index and Ap3 index history for up to 72 hours are used. The resulting linear regression model, currently developed at 45°N, has an unprecedented 30 minute temporal resolution and 3° resolution in longitude and spans the years 2002-2019, the extent of the extreme ultraviolet data provided by the TIMED Solar EUV Experiment (SEE). At this latitude, the RMS error of the model is 1.78, though this number varies depending on the longitude in question. Future work will include application of this model to all other latitudes with the same geographical resolution.