Toroidal convection rolls in the sun a challenge to theory

Abstract

A large-scale circulation in the form of azimuthal (east-west oriented) rolls has been discovered in the convection zone of the Sun (Ribes et al.0, 1985; Ribes, 1986). The characteristics of the global circulation (for example orientation, number, lifetime and so forth) are quite different from those of meridional cells (oriented parallel to the solar axis) which has been predicted by theory (e.g. Glatzmaier, 1985). This raises the important question as to whether or not the newly-discovered azimuthal rolls contribute to the transport of heat from the deep interior of the Sun to its surface. Here we report new results that exhibit the convective nature of the azimuthal rolls. These are based on 22 years of observation of the roll pattern (Ribes, 1986), a 11 year sequence of solar diameter measurements (Laclare, 1987), and four years of luminosity measurements (Willson et al., 1981). The first indication is provided by the distribution of solar activity, which frames the roll pattern rather than being superimposed on it. The second hint comes from a temporal association that exists between the onset of new rolls and the luminosity and diameter oscillations with a period of 980 days.