SOLAR LIMB DARKENING 1986-1990 - (LAMBDA-LAMBDA-303-NM TO 1099-NM)

The Sun's limb darkening was observed repeatedly between the 1986 minimum and the 1990 maximum of solar activity. Systematic variations, which could depend either on the momentary activity and/or the phase in the solar cycle, were not detectable, either at continuum wavelengths or in two broad-band spectral intervals. Completely irregular variations, which concern not only individual, successive scans (due to granulation, etc.), but also the daily and seasonal averages, are usually less than 1%, but can reach occasionally 2% or even more. Minor east-west asymmetries even in the seasonal means seem to be well established, mainly for lambda < 400 nm. The final, mean limb-darkening coefficients agree basically with those published by Pierce and Slaughter (1977) and Pierce, Slaughter, and Weinberger (1977), but show a much lower scatter when plotted against wavelength.