Rocket measurements of modifications of the ionospheric plasma of the F-layer produced by the heating installation in Northern Norway

An installation for heating the ionosphere was built approximately 15 km southeast from Tromso in Norway. The installation includes 12 transmitters having each a maximum power of 120 kW. A frequency range from 2.75 to 8.0 MHz can be covered. Instabilities, related to the irradiation of very intense radio waves of appropriate frequency and polarization in the MHz-range, lead to a number of modifications in the lower vicinity of the reflection level of the heating waves. Fejer (1979) has provided a detailed report concerning the occurring modification processes. Measurements performed with diagnostic instruments located on the ground are, however, subject to certain restraints. The present investigation is, therefore, concerned with the conduction of in-situ measurements with the aid of instrumented rockets. During the time from October to December 1982, four rockets have been launched from Andoya either in the morning or in the evening, on occasions when the ionosphere was very quiet. The obtained data and their significance are discussed.