Solar Physics Division Meeting 2000, June 19-22
Session 1. Helioseismology, Magnetic Fields, Chromosphere and Transition Region
Display, Chair: C. U. Keller, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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[1.21] Plasma Flows within and around Sunspots

T. A. Bai, P. H. Scherrer (Stanford University)

It is essential to know plasma flows within and around sunspots for understanding the evolution and stability of sunspots. By analyzing data obtained by the Michelson Doppler Imager aboard SOHO, we have studied plasma flows within and around four sunspots in the decay phase. We have confirmed the existence of a downward component in the Evershed flow, which has been recognized until recently, mainly as horizontal outflows in the penumbra. The downward component reaches its peak value of about 500 m/s near the outer edge of the penumbra. Additionally, we have discovered plasma flows within umbrae. In two sunspots (in AR 7981 and AR 8194), we have found evidence for radial inflows within the umbra, which are in the opposite direction of Evershed flows. In two other sunspots under this study (in AR 8402 and AR 8403), we have found evidence for outflows within the umbra. The speeds of such horizontal flows are about 300 m/s.


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