KINEMATIC MODELS OF SUPERGRANULAR DIFFUSION ON THE SUN

We develop kinematic models of diffusion generated by supergranulation at the solar surface. These models use current observations for the s ize, horizontal velocity, and lifetime of supergranules. Because there is no observational description of the appearance and disappearance o f supergranules, we investigate models using several plausible evoluti on processes, including the effect of different lifetime distribution functions for the cells. The results are quite insensitive to the meth ods chosen to replace old supergranules, the distribution of cell life times, and even the cell lifetime itself, for mean lifetimes between 1 5 to 30 hr. Calculated diffusion coefficients range between 500 and 70 0 km(2) s(-1), in agreement with the best fit diffusion coefficients u sed by Sheeley and his collaborators to model the large-scale distribu tion of magnetic fields over the solar surface. However, our models do not explain the field distribution in plage, and they predict that vi rtually all the strong field in quiet Sun exists in relatively isolate d clumps, We suggest possible mechanisms for the creation of plage and the bright network seen in quiet Sun.