On the difference between the average values of B r ² in the Atlantic and Pacific hemispheres

Recent work on reversals of the earth's magnetic field [ Clement , 1991; Constable , 1992; Laj et al., 1991; Runcorn, 1992] and work on low rates of change of the radial magnetic field, B r , in the Pacific hemisphere (see Jacobs [1994] page 8, for a summary) suggest that the statistics of B r differ between the Pacific and Atlantic hemispheres. The question of statistical invariance of the magnetic field is interesting in its own right [ Courtillot et al, 1992], and we study this hypothesis by investigating the statistical significance of the difference between the average value of B r ² in the Atlantic and Pacific hemispheres at three different radii. The differences between the average value of B r ² in the Atlantic hemisphere and the average value of B r ² in the Pacific hemisphere at all three radii are incompatibly large with two statistical models of B r . The differences are incompatibly large at two of three radii when a third statistical model is used. The results suggest that further work on the statistical properties of B r is warranted and provide another test for normality of spherical harmonic coefficients.