Reply [to “Variations of total solar irradiance produced by structural changes in the solar interior”]



In their Comment to my article [Sofia, 2004], PFoukal and H. Spruit imply that the surface magnetic effects alone can explain the observed solar cycle variations of (1) the low- and medium-degree p-mode oscillation frequencies; (2) the f-mode oscillation frequencies; (3) the solar radius; (4) the solar photospheric temperature; and (5) the solar irradiance.

In fact, it is hard for surface magnetic effects to explain most of these variations since they are not supposed to change the internal structure of the Sun, and these observations require some internal structure readjustment. These failures are further increased by recent observations which show that the faculae, which are supposed to increase irradiance, can actually be dark in the disk center when measured in the continuum wavelengths [Kuhn et al, 1998]. Moreover, if Willson's reconstruction of the total solar irradiance history, which shows a difference in the level at the last two minima, is correct [Willson, 1997],we find another feature of the TSI that is difficult, if not impossible, to explain on the basis of surface magnetic effects alone.