[en] A planned coodinated study of the complex processes in the ionosphere is briefly discussed. Selected time intervals will be used to perform the coordinated data analysis, to reach quantitative agreement between all measurements and theoretical model results, to identify the dominant physical processes, to retrieve realistic information concerning mass fluxes, momentum and energy, and to investigate certain energetic aspects of the morphological results in more detail. The selection intervals, topics to be studied, data base to be acquired, and models to be used are described

[en] The generation of large-scale electric fields and currents due to the dynamo process has been reviewed, especially for the low latitudinal ionosphere of the Earth. Tidal motions in the atmosphere are described in brief. The kinematic dynamo giving rise for the three-dimensional Sq-current system and the electric field distribution disregarding the recoupling effect of the plasma on the neutral wind velocity field has been described. Taking additionally into account the dragging of neutrals by ions (hydromagnetic dynamo theory) results in good agreement of the theoretical distribution of the zonal electric field with the experimental data. (author)

[en] At the end of the sixties it became obvious that two-dimensional dynamo models can explain nearly all facts, which had been found morphologically for mean annual Sq-fields. During the recent decade new or improved methods to measure electric fields (e.g. incoherent sy.ter facilities) and to investigate great data files have been developed. New informations received with these methods about the existence of regular variations of the Sq-field in dependence on season and universal time andtabout the electric field have been summarized in Section 2. All attempts to describe also these variations with a two-dimensional dynamo mooel did not lead to any success, but showed a strong theoretical over-estimation of the asymmetries. Therefore, it must be concluded that three-dimensional plasmaspheric current systems, taking into consideration the coupling between both hemispheres along the high-conducting magnetic field lines, are needed in order to explain the regular variations of the Sq-field. The basic equations for two- and three-dimensional dynamo models, different methods for the solution of these equations and the resulting models from different authors are compiled and discussed (Section 3). Based on all morphological and theoretical results a plasmaspheric-ionospheric current system has been constructed and some properties of the plasmaspheric field-aligned current distribution, have been derived. (orig.)

[en] The variations of the parameter of the ionospheric electron gas have been studied for an interval (April 3-5, 1979) being characterized by strong changes of the parameter of the interplanetary medium. On April 3 the system 'interplanetary medium-magnetosphere-ionosphere' was activated by a southward turning of the IMF-Bz-component (-10nT) and reacted in the well-known manner by generating a magnetospheric storm with the negative phase of the ionospheric storm on April 4. On April 5 the system was activated in quite another manner by a strong northward IMF-Bz-component (+25nT) and increased solar wind pressure. As a reaction of the ionosphere a region of enhanced electron density in the F2-layer-maximum developed in midlatitudes on the dayside around noon, being superposed on the continuing negative phase of the ionospheric storm. Very strong latitudinal electron density gradients existed on the dayside in subauroral latitudes, and the altitude of the electron density maximum shifted upwards by more than 100 km in subauroral and medium latitudes. (author)