AAS 204th Meeting, June 2004
Session 37 Solar Magnetic Fields and the Photosphere
SPD Poster, Tuesday, June 1, 2004, 10:00am-7:00pm, Ballroom

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[37.12] Supergranule Diffusion and Active Region Decay

D.H. Hathaway (NASA/MSFC/NSSTC), D.P. Choudhary (NRC/MSFC/NSSTC)

Models of the Sunís magnetic dynamo include turbulent diffusion to parameterize the effects of convective motions on the evolution of the Sunís magnetic field. Supergranules are known to dominate the evolution of the surface magnetic field structure as evidenced by the structure of both the active and quiet magnetic network. However, estimates for the diffusivity attributed to supergranules differ by an order of magnitude - from about 100 km2/s to more than 1000 km2/s. We examine this question of the diffusivity using three different approaches. 1) We study the decay of more than 30,000 active regions by determining the rate of change in the sunspot area of each active region from day-to-day. 2) We study the decay of a single isolated active region near the time of solar minimum by examining the magnetic field evolution over five solar rotations from SOHO/MDI magnetograms obtained at 96-minute intervals. 3) We study the characteristics of supergranules that influence the estimates of their diffusive properties Ė flow speeds and lifetimes as functions of size ~V from SOHO/MDI Dopplergrams.


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Bulletin of the American Astronomical Society, 36 #2
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