DEVIATION OF THE PRINCIPAL MAGNETIC FIELD OF THE EARTH FROM THE DIPOLE MODEL

Abstract

Analysis of the position of vertical magnetic poles (VMP) based on the annual mean declination and inclinations, measured at observatories over the last 150 years, has shown considerable regional deviations in measurements of both their position and the rates and directions of polar drift. The authors attempted to determine whether a purely formal determination of a single 'optimum size of such regions for the entire earth was possible. This optimum size might, among others, be determinable by constructing a plot of distances between VMP's (ΔVMP) versus the distance between observatories £. The 1958 epoch was chosen as the most representative in terms of the number of observatories in operation. For each of these observatories a plot was constructed of this relationship, consisting of 180 points, then the mean distances were calculated between VMP's for inter-observatory distances of 1 to 100, 0 to 200, ..., 0 to 20,000 km. Study results are discussed.