Comparison of the foF2 Longitude Distribution in the Nighttime Low-Latitude Ionosphere Inferred from Intercosmos-19 Data with IRI and Ground-Based Data

摘要

The foF2 longitude distribution in the nighttime low-latitude ionosphere measured onboard Intercosmos-19 has been compared with IRI and ground-based data. It has been obtained that the IRI model with the CCIR coefficients somewhat describes the small-scaled longitude structure of the low-latitude ionosphere derived from Intercosmos-19 data but with the amplitude much lower than the actual amplitude. The foF2 longitude variations at low latitudes in the IRI model with the URSI coefficients are too smoothed. Intercosmos-19 data have demonstrated that it is impossible to adequately describe the longitude variations in the nighttime low-latitude ionosphere using only two harmonics (as in the IRI-URSI model). At least five harmonics are apparently needed for such a description. The foF2 variations along the magnetic equator at the ground-based stations are closer to the distribution obtained from Intercosmos-19 data than to the IRI model.