Plasmaspheric electron content derived from GPS TEC and digisonde ionograms Original Research Article

The plasmaspheric electron content is extracted from the residuals of GPS-derived TEC measurements from estimates of the electron content obtained by a ground-based ionosonde at Athens (38°N, 23.5°E) over a 12-month time period. The plasmaspheric electron content exhibits a diurnal variation with a morning minimum and an evening maximum, which can be explained in terms of ionospheric–plasmaspheric ionization exchange, while its response during geomagnetic storms shows clear signature of depletion and successive replenishment following the storm activity. Finally, the comparison of the ionospheric and total slab thickness variation and the estimate of the percentage contribution of the plasmasphere to the total electron content demonstrates the importance of the plasmasphere in ionospheric studies, especially during night hours.