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Session 17 - Magnetic Fields II.
Oral session, Tuesday, July 01
Ballroom A, Chair: Paul Charbonneau

[17.01] Surface Flows in Active Regions

T. Bai, R. S. Bogart, P. H. Scherrer (Stanford Univ.), T. D. Tarbell (Lockheed-Martin)

Plasma flows around sunspots must influence the stability and development of sunspots. We have been studying photospheric flows around sunspots by analyzing dopplergrams and magneto- grams obtained by the MDI (Michelson Doppler Imager) aboard SOHO. We have found some interesting phenomena. First, during the growing phase of an active region, plasmas around sunspots seem to draft downward with a speed of order of 100 m/s. Second, during the decaying phase of an active region, plasmas around sunspots flow outward. Outflow speeds range up to several hundred m/s. Such outflows are prominent during the decaying phase of a long-lived big active region. Third, there is evidence for flows within sunspots. Such flows are presumed to be along magnetic field lines. We will present the details of these results and discuss their implications on the dynamics and stability of sunspots.

MDI research is supported by NASA contract NAG5-3077 at Stanford University.


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