Observations of the solar mean magnetic field at the Sayan Observatory during 1982?1984

Abstract

This paper presents some results of observations of the mean magnetic field of the Sun as a star (SMMF) at the Sayan Observatory during 1982-1984. A description of the instrument is given, as well as some major points in the technique of data acquisition and treatment such as calibration, zero-level control, etc. The comparison of a new SMMF series with observations from the Wilcox Solar Observatory showed a high correlation between the two series (p = 0.88) but with a rather great difference in amplitudes. We discuss time variations of SMMF, both long-term caused by the magnetic field evolution with the activity cycle and those of shorter time-scales caused by solar rotation.

On stability of rotation of the mean magnetic field of the Sun

“…The limb darkening enters B as a weighting function, together with additional coefficients responsible for rotation, red shift of the spectral line near the limb, correlation of field strength with the line contour variations and photosphere brightness, etc. (see details in Scherrer 1973;Grigoryev et al 1983;Grigoryev & Demidov 1987;Kotov et al 1998b). …”

“…The agreement improves if one introduces the coefficient α = 0.62, equal to the ratio of the standard deviations of the two time series (see Table 2). For several days, or during a few consecutive days, however, large differences in B values, exceeding errors of measurements, will still exist; they cannot be corrected by the factor α (the typical errors are: ±0.15 Gs for CrAO and ±0.05 Gs for WSO; on the accuracy of measurements see Grigoryev & Demidov 1987;Kotov et al 1998a. The equation of linear regression for n = 51 pairs of the MMFS values obtained "simultaneously", i.e.…”

“…A wide-spreaded opinion that data obtained by some intruments are more accurate than those from other instrument (see Grigoryev & Demidov 1987;Kotov et al 1998a) seems to be questionable. Notice for instance that the S values of three observatories -CrAO, MWO and SO (see Table 2) -are very close to each other and to their average value 0.70 Gs, whereas the Stanford measurements show S = 0.41 Gs, i.e.…”

“…4, where it seems worthwhile to note its non-harmonic form and asymmetry between positive and negative halfwaves. The latter might be associated with (a) quadrupole component of global solar magnetic field which can be comparable sometimes, in magnitude, with dipole component and can introduce significant deviations from a pure harmonic curve, and (b) the magnetic asymmetry of the Sun as a whole (see Severny 1968;Wilcox 1972;Kotov & Levitsky 1985;Grigoryev & Demidov 1989).…”

“…see Scherrer et al 1977b), 4) the Sayan Observatory of the Solar-Terrestrial Physics Institute (SO, Irkutsk; measurements were begun in 1982 by Grigoryev & Demidov 1987).…”