Abstract
A magnetometer array study in central Australia has revealed a large area over which the vertical-field response-arrows at substorm periods point consistently towards an electrical conductivity anomaly in south-west Queensland. For this area of smooth vertical-field response, estimates of the electrical conductivity profile in the earth have been made by analysis of two magnetically quiet days, using horizontal gradients of the quiet daily variation as measured across the array area. A simple “substitute conductor” method has been used to invert the data. The results indicate that beneath this part of the continent the electrical conductivity is of order 0.1 to 1.0Sm-1 at a depth of order 300 to 400km, confirming the more general results of global analyses, which use data from more widely-separated observatories.
