Solar brightness variability, illuminating paper

Tim suspects this paper is important even though it is based largely on modelling. It says the intensity of spectral lines etc. are very important in variability, ultra-violet particularly, moreover there is counter sunspot cycle. This fits with where I think we are going on understanding solar terrestrial linkage.

The role of the Fraunhofer lines in solar brightness variability
A. I. Shapiro S. K. Solanki, N. A. Krivova, R. V. Tagirov, and W. K. Schmutz

Astronomy & Astrophysics, 2015, open access with free registration.

ABSTRACT
Context. The solar brightness varies on timescales from minutes to decades. A clear identification of the physical processes behind such variations is needed for developing and improving physics-based models of solar brightness variability and reconstructing solar brightness in the past. This is, in turn, important for better understanding the solar-terrestrial and solar-stellar connections.
…

Results. We show that the variations in Fraunhofer lines define the amplitude of the solar brightness variability on timescales greater than a day and even the phase of the total solar irradiance variability over the 11-year cycle. We also demonstrate that molecular lines make substantial contribution to solar brightness variability on the 11-year activity cycle and centennial timescales. In particular, our model indicates that roughly a quarter of the total solar irradiance variability over the 11-year cycle originates in molecular lines. The maximum of the absolute spectral brightness variability on timescales greater than a day is associated with the CN violet system between 380 and 390 nm.

I am particularly interested in the peculiarities which run counter to the obvious visual proxy of sunspots, which do nothing as such. The sun is far more complex, magnetics and spectral variation. In this case hot details radiate.

UV change is important both as stimulating the highly radiatively active earth O₃ which also has an atmospheric window, right through into water. I’ve not see long datasets on this UV, maybe readers know.

Post by Tim