A global view of the role of acceleration processes in solar-terrestrial coupling as provided by the ISTP theory and ground-based experiments

Present global simulations of the Earth's upper atmosphere and magnetosphere, which have been developed under the auspices of the International Solar Terrestrial Physics (ISTP) Program, can provide an effective, near-quantitative, global view of the role of acceleration processes in the transport of energy, momentum, and mass from the solar wind, through the magnetosphere, and to their final deposition in the upper atmosphere. In addition, ground-based experiments can provide not only more realistic inner boundary-conditions for the global MHD magnetosphere simulations, but give improved estimates of the roles of magnetospheric acceleration processes in the upper atmosphere. An overview of a detailed case study of a series of events which occurred during 19-20 May 1996 will be used to illustrate the power of theory and ground-based observations to complement spacecraft observations in providing a global view of acceleration processes. The period from 0100 UT 19 May to 0300 UT 20 May 1996 was chosen as an illustrative case since it contains times of steady solar wind conditions, and periods of slow variations in the IMF followed by sudden changes in the IMF. These conditions are near ideal for global simulation-observation comparisons. It also has two distinct substorms at 2020 UT 19 May and 0035 UT 20 May. The slow changes in the IMF followed by the rapid changes provided excellent conditions for comparing theoretical predictions of the global effects of acceleration processes and observations from ground-based and spacecraft experiments.