[en] The Chatanika radar is a pulsed radar system with the possibility of transmitting two pulses of different length. The observational procedures used in deriving the large scale ion velocity and currents in the ionosphere are discussed at some length. Discussion of the movement of the ionization in the auroral E and F regions shows how the electric fields may be derived. The derivation of the neutral wind in the E-region is then discussed. The paper concludes with a discussion of electrical conductivities and currents in the upper atomsphere. (JIW)

[en] The European Incoherent Scatter Radar in the Auroral Zone (EISCAT) is an intereuropean organization planning to install an incoherent scatter radar system in Northern Scandinavia. It is supported by Finland, France, Norway, Great Britain, Sweden and West Germany, and its headquarters is in Kiruna, Sweden. The radar is planned to be operating in 1979. In order to introduce students and young scientists to the incoherent scatter radar technique, a summer school was held in Tromsoe, from 5th to 13th June 1975. In these proceedings an introduction to the basic theory of fluctuations in a plasma is given. Some of the present incoherent scatter radars now in use are presented and special considerations with respect to the planned EISACT facility are discussed. Reviews of some recent results and scientific problems relevant to EISCAT are also presented and finally a presentation of some observational techniques complementary to incoherent scatter radars is included. (Ed.)

[en] Various observation schemes to obtain results suitable for the estimation of physical parameters of the ionosphere by incoherent scatter observations are discussed. Observation schemes to estimate electron density from both power and Faraday rotation measurements are first discussed. The following section addresses the problem of measuring the plasma autocorrelation function and hence the spectral distribution of the plasma fluctuations. The last section deals with a general procedure for the estimation of ionospheric parameters from the observational results. (Auth.)

[en] Both Kiruna and Sodankylae will use four UHF receivers operating at 933 MHz since there are two antennas planned at each site, each equipped with two horns. In Tromsoe only one UHF receiver is required which makes a total of nine UHF receivers. The VHF system operating at 224 MHz is monostatic. Thus only one VHF receiver is required and it will be installed in Tromsoe. The noise specifications for the UHF receivers are presented and a discussion of their design is given. The VHF receiver will employ a transistor amplifier whose output will be mixed down to 1 00 MHz and the UHF receiver used for further amplification. The systems for frequency generation and timing are also discussed and finally the cost estimates are presented. (JIW)

[en] A general expression is derived for the differential scattering cross-section of radio waves scattered by the thermal fluctuations of electron density in a plasma. The derivation is based on the test particle principle. (Auth.)

[en] The scattering of electromagnetic (EM) waves by a single electron is developed from first principles. The result is used to derive the relationship of the scattered power spectrum to the spacetime Fourier transform of the electron density fluctuations in a plasma. (Auth.)

[en] A discussion is given of the currents that flow in the high latitude ionosphere and in the magnetosphere and problems that can be investigated using the EISCAT facility are indentified. Topics discussed are the magnetic effects of the combined ionospheric-magnetospheric current systems, the relation between the currents and electric fields, and mechanisms for driving the large-scale and small-scale currents. (Auth.)

[en] Scattering of radio waves in the range 20 to 2000 MHz, from field-aligned irregularities in the auroral E-region is known as auroral clutter, radio aurora, auroral reflections or auroral echoes. The general characteristics of auroral clutter are first briefly summarized. The physical nature of the processes which give rise to this special type of radio propagation is then reviewed. Finally, the influence of auroral clutter on the EISCAT experiments is discussed. It is concluded that no interference from auroral clutter should be expected on the EISCAT UHF (933,5 MHz) incoherent scattered signals. There seems to be a margin of at least 10-20 dB against auroral clutter at this frequency for the three different receiving sites. However, for the VHF EISCAT frequency at 224 MHz there is certainly a risk of interference from strong auroral clutter. In order to avoid interference from strong auroral clutter at this frequency the requirements to the sidelobes will be close to 55 dB below the main lobe of the approximately vertical antenna which is screened from the northern horizon by more than 10 degrees at Tromsoe. (Auth.)

[en] The structure and dynamics of the thermosphere are reviewed in a general way, in relation to the properties of the ionospheric F region. Following a resume of F region theory, the paper discusses qualitatively the energy input to the thermosphere and F region. Some suggested thermospheric models and the wind patterns associated with them are then described. Such F region phenomena as seasonal, storm and semi-annual variations are also discussed. Some possible applications of EISCAT to studies of these phenomena are mentioned. (Auth.)

[en] During the intense solar-particle event in August 1972 the SRI incoherent-scatter radar at Chatanika, Alaska and the Lockheed 1971-089 polar-orbiting satellite made a large number of simultaneous measurements in the polar cap. Energetic-particle fluxes measured by the satellite were transformed into altitude profiles of electron production rate, Q. These profiles were combined with radar-derived altitude profiles of electron density, N, to obtain altitude profiles of effective recombination coefficient α = Q/N². From the most intense period of the event, 4-6 August, 18 sets of coordinated measurements have been reduced to α-profiles. The selected profiles provide a description of effective recombination coefficient over a full spectrum of local time, a range of solar zenith angle, chi from 50⁰ to 98⁰, and an altitude range from 59 to 89 km. Synoptic behaviour of this important PCA parameter is thus presented for the first time. (Auth.)