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J. F. Tucker, H. B. Snodgrass (Physics Dept. Lewis & Clark College)
Analysis of the Pearson correlation amplitude as a function of latitude, lag in longitude and time separation of correlated magnetograms reveals interesting mean properties of the magnetic field features seen in the photosphere. Small features decorrelate after a few days, but correlations persist at all latitudes for lag times spanning several rotations, revealing the ubiquitous presence of concentrated aggregates of small features that (1) differentially rotate like the small features, (2) have very long lifetimes, and (3) have areal sizes an order of magnitude larger than supergranules. These ``meso-scale" features comprise the unipolar plumes extending poleward from the active regions, and the more rigid rotation of the plumes stems from the poleward meridional drift and random walk of these features. The random walk is consistent with a diffusion constant of 600 Km2 s-1, but these features are too large for this to be propelled by supergranular convection. We discuss the evolution of the properties and motions of these features, or aggregates, during the activity cycle. This work is supported through NSF Grant ATM98-14145.