The Fourier power spectra of geomagnetic component values, synthesized from spherical harmonic models, have been computed for circular paths on the Earth's surface. They are not found to be more useful than is the spectrum of magnetic energy outside the Earth for the purpose of separating core and crustal sources of the geomagnetic field. The Fourier power spectra of north and east geomagnetic components along nearly polar great circle paths exhibit some unusual characteristics that are

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... d by the geometric perspective of Fourier series on spheres developed by Y. K. Yee.