VORTICITY AND DIVERGENCE IN THE SOLAR PHOTOSPHERE

We have studied an outstanding sequence of continuum images of the sol ar granulation from Pic du Midi Observatory. We have calculated the ho rizontal vector flow field using a correlation tracking algorithm, and from this determined three scalar fields: the vertical component of t he curl, the horizontal divergence, and the horizontal flow speed. The divergence field has substantially longer coherence time and more pow er than does the curl field. Statistically, curl is better correlated with regions of negative divergence-that is, the vertical vorticity is higher in downflow regions, suggesting excess vorticity in intergranu lar lanes. The average value of the divergence is largest (i.e., outfl ow is largest) where the horizontal speed is large; we associate these regions with exploding granules. A numerical simulation of general co nvection also shows similar statistical differences between curl and d ivergence. Some individual small bright points in the granulation patt ern show large local vorticities.