Variations of the interplanetary and solar magnetic fields

The authors determine time variations of the interplanetary magnetic field (IMF) observed near the earth and of the mean magnetic field of the sun seen as a star (SMMF) for 1968-1979. All the values of IMF and SMMF were 28-day averaged to eliminate the dependence on solar rotation; also the yearly means were calculated. It is shown that in contrast to the yearly average magnitude of the IMF which is almost constant throughout the solar cycle, that of the SMMF changes markedly from year to year (by 3-4 times). The analysis reinforces the previous conclusion (1981) on the presence of a significant annual variation in the SMMF with amplitude of about 0.1 Gs. It is suggested that some asymmetry of the global magnetic field of the sun in inertial (with respect to stars) space can be responsible for this annual effect as observed from the earth. The annual wave in the IMF magnitude is only marginally significant, ⪉3%, demonstrating once more quite different behaviour of the IMF and SMMF on a month-year time scale. The discrepancy is thought mainly to be the result of different averaging of two physical fields.