Potential Predictability and Forecasting of the State of the Field of Anomalies of the Total Electron Concentration from Observational Data

An attempt is made in this study to evaluate the potential predictability of the TEC field (its deviation from the weekly average) at hourly time scales based on observational data. The method is based on the calculation of the distance between the group of observations and its subsample (group of analogues) contaning pairs of points separated in time but at minimum distance from each other. The time of potential predictability is defined as the time at which the distance between the two groups becomes close to the root-mean-square distance over the archive of observations. Calculations performed for the TEC SDDIS NASA data archive give the predictability time for anomalies within 6–12 h. Strong anomalies of the TEC field are characterized by the highest predictability; the predictability is maximal for the winter hemispheres and in years of high solar activity (1999–2004 and 2011–2015). These conclusions are confirmed by the forecasts based on the simplest empirical linear dynamic stochastic model. The forecasting calculations also show that there are statistical relationships between the predictability time and the minima/maxima of daily values of the F10.7 and ap indices.