The Earth’s Ionosphere-Thermosphere-Electrodynamics (I-T-E) system varies markedly on a range of spatial and temporal scales and these variations have adverse effects on human operations and systems, including high-frequency communications, over-the-horizon radars, and survey and navigation systems that use Global Positioning System (GPS) satellites. Consequently, there is a need to elucidate the underlying physical processes that lead to space weather disturbances and to both mitigate and forecast near-Earth space weather. The meteorologists and oceanographers have shown that data assimilation models are superior to global physics-based models for specifications and forecasts, but only during the last 15 years have they been used for near-Earth investigations as more global (space and ground-based) measurements became available. Although data assimilation models produce better specifi...

During the period 5-13 October 1984 a coordinated solar-terrestrial data base was acquired to develop a comprehensive understanding and an associated predictive capability for the cause-effect relationships which control the global-scale ionosphere. The effort, the first in a series of continuing investigations in a program called SUNDIAL, combined modelling of the ionospheric, magnetospheric, and thermospheric domains with a measurements activity that included a network of ionospheric monitoring stations at high-, middle-, and low latitudes in the American, European/African, and Asian/Australian sectors. Solar, solar wind, interplanetary, and geomagnetic data were also obtained through the NOAA Space Environment Services Center. The period began with nearly two full days of typically quiescent solar mínimum conditions, with the night of the 6th marking a transition to a substantial inc...