Each satellite is equipped with a magnetometer having 48 nT resolution as part of the avionics which provides a means to detect the magnetic deflections associated with the auroral currents.

One can build up an point-mosaic 'image' of the auroral oval by combining the data from the large number of point measurements.

Figure 1. POLAR-VIS image of the auroral oval with schematic Iridium satellite orbit tracks overlaid in blue. Magenta dots represent approximate locations of Iridium satellites at a given instant of time. The tracks show that the orbital coverage provided by the Iridium constellation provides global coverage of the polar region.

Figure 1

Figure 2. Schematic view of a satellite (green) passing through pairs of field aligned currents associated with each crossing of the auroral oval. Locally, large scale currents (blue) are approximately sheets of current which close in the underlying ionosphere. This current system produces the magnetic perturbations (red arrows) at the satellite altitude. It is these perturbations which are detected by the Iridium satellite system magnetometers.

Figure 2