LOWER IONOSPHERE AT MIDDLE LATITUDES - ITS MORPHOLOGY AND RESPONSE TOMETEOROLOGICAL AND SOLAR-TERRESTRIAL ACTIVITY DURING THE DYANA CAMPAIGN 1990

A large number of radio wave absorption, f(min), and IPHA data measure d in Europe and East Asia are investigated over the DYANA campaign per iod (1 January-31 March 1990) from the point of view of their response to meteorological and solar/geomagnetic forcing, of winter anomaly, a nd of a brief description of the state of the lower ionosphere on rock et salvo days. European mid-latitudinal measurements of electron densi ty are briefly mentioned. The meteorological/solar control of the mid- latitudinal lower ionosphere during DYANA is considerably weaker than during MAP/WINE (winter 1983/84), but is evidently stronger than durin g MAP/SINE (summer 1987). The most distinct feature of the DYANA winte r is a quite different response of the mid-latitudinal lower ionospher e to meteorological variability (namely to the 10 hPa North Pole tempe rature-indirect characteristics of a global state of the polar vortex) in the first and second halves of the DYANA period. The winter anomal y displays an expected magnitude and pattern during the DYANA winter. There is an expected weaker response of the lower ionosphere to the st rong minor stratospheric warming of the first half of February. All th ree rocket salvos at Biscarosse (CEL) were carried out when the state of the lower ionosphere was within the range of normal (non-extremal) conditions. Various rocket salvos at Andoya took place on days of cons iderably different conditions in the lower ionosphere at higher mid-la titudes. Partial reflection measurements at Nizhny Novgorod show a cle ar tendency to a decrease of the electron density gradient between 70 and 80 km during March 1990.