抄録
In the past two years there have been major advances in two areas. Firstly the nature of the DPY current system in the region of the polar cleft (cusp) has been more clearly defined through the use of the polar orbiters Triad and ISIS 2. It was now clear that field-aligned currents bound an ionospheric electrojet whose direction of the flow is regulated by the polarity of the By component of the interplanetary magnetic field. A second major advance has been in the development of comprehensive three-dimensional current system models which are capable of reproducing high latitude magnetic field perturbations. Work of this nature has been carried out in the U. S. S. R. and Canada, while investigations as to the driving mechanism for the current systems have been carried out in the U. S. A. and in Japan. Considerable progress continues to be made in defining the phenomonology of parallel electric fields in the altitude range 2, 000-10, 000km and in the development of the theory for explaining the acceleration mechanisms. The STARE radar system has now provided a powerful tool for the study of spatial and temporal variations of ionospheric electric fields; the use of the STARE data together with data from the European magnetometer arrays operating in Scandinavia during the IMS provides an outstanding opportunity to make major breakthroughs in the next few years.
