New input to IRI from the worldwide digisonde network

Electron density profiles derived from Digisonde ionograms at Argentia, Millstone Hill, Wallops Island, Bermuda, Dourbes and Karachi are compared with IRI model prediction. Four months of data for 1989/90 were analyzed. For a number of station/months N(h) profiles were available every 15 or 30 minutes providing a good statistical database for the evaluation of the IRI model in terms of diurnal and seasonal variations. The data presented here are part of the VIM study (Validation of Ionospheric Models) initiated by the URSI Working Group G3 on Ionospheric Informatics.