We present a validation study of southern hemisphere field-aligned current (FAC) distributions calculated from magnetic field perturbation data observed by the Iridium satellite constellation. In contrast to the northern hemisphere, the offset between the geomagnetic pole on which geomagnetic phenomena are centered, and the Iridium orbit plane intersection points becomes important for southern hemisphere studies. We investigate the reliability of FAC reconstruction for all possible offset locations using both spherical harmonic and elementary current system based algorithms. The results show that the accuracy of the reconstructed FAC distributions decreases with increasing offset. For small southern hemisphere offsets the FAC results are found to be accurate while for the medium to maximum offset range the accuracy depends on the FAC configuration. In general, a large offset has little effect for FAC distributions associated with a southward directed IMF and a maximum effect for northward IMF cases. The results also show the offset has no significant effect on northern hemisphere studies.
7th Australian Space Science Conference. Proceedings of the 7th Australian Space Science Conference (Sydney 24-27 September, 2007) p. 110-117