6.3 Flux tubes versus diffuse fields
The foregoing discussion has implicitly assumed that the dynamo process produces a mean, large-scale
magnetic field that then concentrates itself into the flux ropes that subsequently give rise to
sunspots. High-resolution observations of the photospheric magnetic field show that even outside of
sunspots, the field is concentrated in flux tubes (see, e.g., Parker, 1982, and references therein),
presumably as a consequence of convective collapse of magnetic flux concentrations too weak
to block convection and form sunspots. In this picture, which is basically the framework of
all dynamo models discussed above, the mean magnetic field is the dominant player in the
cycle.
An alternate viewpoint is to assume that the solar magnetic field is a fibril state from beginning to end,
throughout the convection zone and tachocline, and that whatever large-scale field there may be in the
photosphere is a mere by-product of the decay of sunspots and other flux tube-like small-scale
magnetic structures. The challenge is then to devise a dynamo process that operates entirely on
flux tubes, rather than on a diffuse mean field. Some exploratory calculations have been made
(e.g., DeLuca et al., 1993), but this intriguing question has received far less attention than it
deserves.
