A New Analysis of the Geomagnetic Sq Field

Abstract

The geomagnetic solar quiet daily variation field, Sq, was analyzed by a new method and the result was compared with that of MATSUSHITA and MAEDA (1965). The new method is intended to avoid errors which occur in harmonic analysis due to the equatorial electrojet of narrow latitudinal width; the magnetic effect originating from equatorial electrojet currents is temporarily omitted until after the spherical harmonic analysis has been performed, and later the effect is added in. Compared with the results obtained by Matsushita and Maeda, it is found that: (1) Spherical harmonic coefficients for the Sq field generally become smaller. (2) Magnitude of the equivalent current systems external to the earth diminishes by 10-20 per cent. (3) The coefficients which are mainly responsible for the jet effect are a16, a110, b16, b110, a27, a211, etc.; they become considerably smaller. In many of these terms the amplitude ratio Emn/Imn of the external to the internal part also becomes smaller. (4) The amplitude ratios, Emn/Imn, for main terms become larger. © 1973, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.