Report from IUGG Assembly: IAGA session on correlation between anomalies of potential fields

Abstract

The convener of the session was R. D. Regan of Phoenix Corporation, Mclean, Virginia, who unfortunately could not himself attend the Canberra meeting because of a schedule conflict. Accordingly he asked P. J. Hood of the Geological Survey of Canada, Ottawa, to chair the session for him. The objective of the session was to examine the correlation between potential field anomalies, and to this end papers which dealt with the theoretical and/or practical aspects of the correlation of local, regional, and planetary gravity and magnetic field anomalies were invited.Six papers were presented during the half‐day session held on the morning of December 14, 1979. The first paper presented was a theoretical one by M. H. A. Hassan and I. A. Eltayeb. They were motivated by the suggestion that the high degree of correlation between the gravitational and magnetic potentials of the earth (such correlation being discovered by Hide and Malin via the use of harmonic analysis) may be due to the presence of small topographical irregularities on the core‐mantle interface. Accordingly, they investigated the motion of an incompressible fluid that flowed over a corrugated solid surface in the presence of a uniform poloidal magnetic field and a toroidal magnetic field which increased from zero in the solid to large values deep into the fluid. The system was rotated uniformly, and they found that the motions set up by the topography traveled deep into the fluid. The gravitational disturbances that were produced by the discontinuity in density at the fluid‐solid interface correlated with the magnetic perturbations (caused by the motion of the fluid) far into the solid. The highest degree of correlation was shown to be approximately +0.79, and this corresponded to a situation in which the magnetic potential was displaced both longitudinally and latitudinally relative to the gravitational one.