The integrated sun as a (magnetic) variable star

Although the source of the solar magnetic cycle is not yet fully understood, it is clear that observed solar variations result primarily from surface manifestations of magnetic field associated active regions. Globally, and at depth in the solar interior, variations of convective efficiency following from magnetic field variations may cause luminosity and diameter changes. The waxing and waning of sunspots and faculae in the photosphere lead to luminosity variations on time scales of days to months, or longer. In the chromosphere magnetically controlled plage leads to a variation of UV flux and line emission such as Ca II H and K. The coronal structure is dominated by background magnetic fields and experiences factor of 2 variations of total mass over the solar cycle. Relative modulation characteristics are remarkably similar from the different atmospheric levels with their unique activity types.