Using the empirical terrestrial magnetospheric magnetic field models of Tsyganenko and Usmanov (TU) and Tsyganenko (T87), we determined the average field-aligned currents (FACs) in the magnetosphere as a function of the Kp index. We identify three major model FAC systems; dayside region 1 (DR1), nightside region 1 (NR1), and nightside polar cap (NPC). The models provide information about the sources of the current systems. Mapped ionospheric model FACs are compared with low-altitude measurements obtained by the MAGSAT spacecraft. We find that low-altitude data can reveal either classic region View the MathML source or more highly structured FAC patterns. We therefore expect statistical results, either obtained from observations or inferred from models, to be averages over temporally and spatially shifting patterns.
