Published online by Cambridge University Press: 12 April 2016
Magnetic fields generated and driven by thermal convection are the primary cause of solar activity. There are many facets of the activity, such as plages, flares, sunspots, coronal heating, and the variation of solar luminosity or irradiance whose nature and cause are understood only partially or not at all, although detailed superficial observational descriptions are available. It is suggested that the inferred 105 gauss azimuthal field bundles may be a direct result of the emergence of Ω-loops to form bipolar magnetic regions on the surface in association with an increase in solar irradiance.