MORPHOLOGY OF THE D-REGIONS AND E-REGIONS AT HIGH-LATITUDES IN THE NORTHERN-HEMISPHERE DURING THE DYANA CAMPAIGN IN 1990

The morphology of the D- and E-regions in the northern hemisphere at l atitudes above 60-degrees-N during the DYANA campaign from 11 January to 16 March 1990 is described on the basis of riometer, rocket and EIS CAT measurements. The campaign was carried out during the sunspot maxi mum year of solar cycle 22 and was aimed at studies of the middle atmo sphere. During the winter anomaly days of the campaign period an incre ased ionospheric absorption measured by a riometer was seen on only on e winter anomaly day, and only at the southernmost station of the riom eter network at latitude 63-degrees-N. The ionospheric absorption did not increase during a stratospheric warming in early February. Both wi nter and autumn anomalies in the ionospheric absorption occurred durin g 1990. The substorm events observed during the campaign period are di scussed and electron density profiles in the D- and E-regions are pres ented for different substorm phases.