Studies of solar magnetic fields

Abstract

Solar magnetic flux data accumulated from the magnetograph of the Mount Wilson Observatory are used to infer average east-west field inclination angles for the interval 1967–1973. In all latitude zones the total flux (∣F ⁺∣ + ∣F ⁻¹∣) measurements indicate that the field is inclined so as to trail the rotation by a small amount. Averaged over the whole disk, this angle is $0\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{^\circ } 8$. No clear pattern may be seen in the variations of this quantity with time in any latitude zone. The individual polarities show some systematic behavior. In the north, the negative (preceding) fields are inclined so as to trail the rotation at all latitudes. The positive fields are inclined toward the rotation by a smaller amount. In the south, a similar situation exists for the fields below 40° latitude, but poleward of 40° the following polarity fields are strongly inclined to trail the rotation. In the north, there has been a gradual decrease of the inclination angles of both polarities during the seven-year interval. At the higher latitudes the sign of the east-west inclinations actually changed during the interval. From an examination of magnetograms it is clear that there are no systematic east-west inclinations of field lines outside sunspots greater than about 30° from the vertical. Cross correlations of the east-west inclination data indicate that equatorward of 40° variations in time of the orientation of fields of the two polarities tend to be parallel, and poleward of 40° these variations are such that the two polarities incline toward or away from each other.