Circular symmetry in the geomagnetic plane for auroral phenomena

Published observational data concerning the configuration and location of the northen and southern auroral zones are reviewed and are compared with circles projected from the geomagnetic equatorial plane, outside the earth, on to the earth's surface along the geomagnetic field lines (in an approximation which includes the five first terms of the spherical harmonic development). Other auroral distance parameters are also compared with these circle projections.

Very good agreement has been found for the northern hemisphere. More accurate data are still needed for those parts of the southern auroral zone which lie over the ocean at a great distance from the Antarctic continent. In the author's opinion the new data confirm that the northern and southern auroral zones are geomagnetically conjugated curves and that they correspond to projections of circles in the geomagnetic equatorial plane on to the earth's surface along the real geomagnetic field lines.