Time-integrated energy budget of a solar activity complex

Abstract

The 0.1–0.3% dips in solar irradiance during disk passages of large sunspot groups suggest the possibility of fluctuations in the solar luminosity. This raises the question of whether the energy not radiated by the dark sunspots is stored within the Sun for long periods of time, or is radiated by faculae during the several-month lifetime of a solar activity complex^1–3. Here we examine the sunspot and facular contributions to luminosity fluctuations due to a solar activity complex over its lifetime from June to November 1982. Both direct, photometric observations of irradiance fluctuations and modelled ‘proxy’ fluctuations based on published sunspot and calcium plage areas are used. We find that the total facular energy excess is between 70 and 120% of the sunspot deficit of ∼10³⁷ erg. Thus, at a minimum, a major portion of the missing sunspot flux is radiated by faculae, and energy balance or even an excess is possible. This work differs from earlier studies^2–9 in that our data cover a longer period of time, more photometric data are included, and our analysis considers the effect of partial occultation of active regions by the solar limb.