A numerical model of the ionosphere, including the E-region above EISCAT

• Published in: Annales Geophysicae
• Main Authors: Diloy, P.-Y., Robineau, A., Lilensten, J., Blelly, P.-L., Fontanari, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Verlag 1996
• Subjects: article; Verlagsveröffentlichung; EISCAT
• Online Access: https://doi.org/10.1007/s00585-996-0191-7; https://noa.gwlb.de/receive/cop_mods_00037838

It has been previously demonstrated that a two-ion (O+ and H+) 8-moment time-dependent fluid model was able to reproduce correctly the ionospheric structure in the altitude range probed by the EISCAT-VHF radar. In the present study, the model is extended down to the E-region where molecular ion chemistry (NO+ and O+2, essentially) prevails over transport; EISCAT-UHF observations confirmed previous theoretical predictions that during events of intense E×B induced convection drifts, molecular ions (mainly NO+) predominate over O+ ions up to altitudes of 300 km. In addition to this extension of the model down to the E-region, the ionization and heating resulting from both solar insolation and particle precipitation is now taken into account in a consistent manner through a complete kinetic transport code. The effects of E×B induced convection drifts on the E- and F-region are presented: the balance between O+ and NO+ ions is drastically affected; the electric field acts to deplete the O+ ion concentration. The [NO+]/[O+] transition altitude varies from 190 km to 320 km as the perpendicular electric field increases from 0 to 100 mV m-1. An interesting additional by-product of the model is that it also predicts the presence of a noticeable fraction of N+ ions in the topside ionosphere in good agreement with Retarding Ion Mass Spectrometer measurements onboard Dynamic Explorer.