Morphology of the D- and E-regions at high latitudes in the northern hemisphere during the DYANA campaign in 1990

Abstract The morphology of the D - and E -regions in the northern hemisphere at latitudes above 60°N during the DYANA campaign from 11 January to 16 March 1990 is described on the basis of riometer, rocket and EISCAT measurements. The campaign was carried out during the sunspot maximum year of solar cycle 22 and was aimed at studies of the middle atmosphere. During the winter anomaly days of the campaign period an increased ionospheric absorption measured by a riometer was seen on only one winter anomaly day, and only at the southernmost station of the riometer network at latitude 63°N. The ionospheric absorption did not increase during a stratospheric warming in early February. Both winter and autumn anomalies in the ionospheric absorption occurred during 1990. The substorm events observed during the campaign period are discussed and electron density profiles in the D - and E -regions are presented for different substorm phases.