Magsat data has been analyzed as a function of the Dst index to determine the first degree/order spherical harmonic description of the near-earth external field and its corresponding induced field. The analysis was done separately for data from dawn and dusk with the following results: dusk external: q01=20.3-0.68 Dst (nT); dusk internal: g01=29987.7+0.240q01(nT); dawn external: q01=18.62 -0.63 Dst (nT): dawn internal: g01=29992.3+0.287q01(nT), where g01 and q01 are the degree 1, zero-order, internal and external coefficiency, respectively, in a spherical harmonic potential function describing the near-earth magnetic field. Comparison with POGO data indicates that the constant term relating q01 and Dst has changed about 20 nT between 1970 and 1980, presumably due to an increase in the average ring current intensity. A local time variation of the external field persists even during very quiet magnetic conditions. Both a diurnal and 8-hour period are present. A crude estimate of Sq current in the ¿45¿ geomagnetic latitude range is obtained for 1966--1970. The current strength, located in the ionosphere and induced in the earth, is typical of earlier determinations from surface data, although its maximum is displaced in local time from previous results.