Anyway the point is — the average regional solar surface flux is drastically variable throughout the day, the year and from year to year — primarily due to water vapor and clouds. (scienceofdoom.com)
We use a TSI model that is solely based on solar surface magnetic phenomena (sunspots and faculae including network). (aanda.org)
The apparently unusual behaviour of the TSI has been interpreted as evidence against solar surface magnetism as the main driver of the secular change in the TSI. (aanda.org)