Secular geomagnetic variations based on spherical harmonic analysises
© Yaremenko L.N, Mischenko U.P., Schenderovskia O.Y.
Results of different spherical harmonic analyses as maps of Z, X, Y components are compared. It is shown how same foci of the secular variations change their maximal values, move in space, differ from each other in their isoline configuration, which depends both on the incompleteness of the observations and, to some extent, on the harmonics used in the analysis. The main foci and the auxiliary foci not always detectable are distinguished. The changes of the centres of foci can reach 20-30° in different analyses, which exceeds the known westward drift of the field.