Comparison of ionospheric ionization measurements over Athens using ground ionosonde and GPS-derived TEC values
Article first published online: 18 DEC 2003
Copyright 2003 by the American Geophysical Union.
Volume 38, Issue 6, December 2003
How to Cite
2003), Comparison of ionospheric ionization measurements over Athens using ground ionosonde and GPS-derived TEC values, Radio Sci., 38, 1105, doi:10.1029/2003RS002868, 6., , and (
- Issue published online: 18 DEC 2003
- Article first published online: 18 DEC 2003
- Manuscript Accepted: 5 NOV 2003
- Manuscript Revised: 23 OCT 2003
- Manuscript Received: 7 JAN 2003
 GPS-derived TEC measurements (GPSTEC) represent the electron content up to 20,000 km, while a new ionosonde technique estimates the ionospheric electron content (ITEC) from ground ionosondes from the bottom of the ionosphere through the peak up to 1000 km. The two independent techniques were applied to determine ITEC and GPSTEC for Athens (38°N, 23.5°E) using the vertical Digisonde observations at Athens and GPSTEC maps produced by DLR/IKN for Europe using GPS measurements. Comparison of the two quantities over a 12-month time period shows a general agreement at daytime and a systematic deviation of ITEC towards lower values during nighttime. The diurnal variation of their residual values (ΔTEC) exhibits a morning minimum and an evening maximum, which can be explained in terms of ionospheric-plasmaspheric ionization exchange. The prominent evening enhancement, observed in all seasons around 1800–2000 LT, is attributed to the plasmaspheric bulge. The application of the superposed epoch analysis method on the daily ΔTEC values for several geomagnetic storms showed a rapid decrease of ΔTEC just after the storm initiation and a consecutive increase over a time period of 9 days, a behavior that is consistent with the plasmaspheric depletion and successive replenishment following storm activity. The daily variation of the ionospheric slab thickness is compatible with the variation of the thermospheric temperature within a day. Concerning the total slab thickness, this behavior is altered by the nighttime increase, which is most prominent in winter, and it is due to the lowering of the O+/H+ transition height. In summary, this analysis presents additional proof that the residuals ΔTEC = GPSTEC − ITEC provide information about the qualitative characteristics of the plasmaspheric dynamics as deduced from their diurnal behavior and their variation during geomagnetic storms.