A study of solar photospheric limb-darkening variations

The authors have obtained regular observations of photospheric limb darkening, using the McMath Solar Telescope, to study possible slow changes in the global temperature structure, in T<SUB>eff</SUB>, and in the ultraviolet continuum flux from the quiet Sun. This paper reports on the analysis of data obtained on 15 days between 1980 September and 1982 December in a continuum window at λ4451. There are no variations of global limb darkening exceeding 0.1% at the 99% confidence level. The implications of these measurements for slow changes in solar luminosity, convection zone structure, and ultraviolet flux are discussed.