Morphology of the southern radio auroral zone

Abstract

Observations of the radio aurora were made from Halley Bay, British Antarctic Territory, during the IQSY using a system of three rhombic aerials at a frequency of 71.3 MHz. The geometry of the echo region observable from Halley Bay is such that, with the aerial system used, radio aurora could be observed frequently over the range of geomagnetic latitudes 67–71.5°S. Diffuse and discrete echoes were distinguished in the analysis of the film records and the distributions of these types of radio aurora over the above latitude range were deduced as functions of universal time and K p . The two types of radio aurora were found to occupy different zones which overlap close to the midnight meridian. Further evidence is presented which suggests that these zones are ‘ovals’ which also overlap near the noon meridian. These zones are compared with the spiral patterns which have been deduced for several other upper atmospheric phenomena. It is suggested that the diffuse and discrete radio auroras may be associated with proton and electron precipitation respectively and that charge separation in the magnetosphere may produce the observed zone pattern.