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Astron. Astrophys. 364, 829-834 (2000)


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Small-scale flow field in a sunspot penumbra

W. Schmidt and R. Schlichenmaier

Kiepenheuer-Institut für Sonnenphysik, Schöneckstrasse 6, 79104 Freiburg, Germany (wolfgang,schliche @kis.uni-freiburg.de)

Received 15 May 2000 / Accepted 1 September 2000

Abstract

We have measured velocity maps of a round sunspot near the center of the solar disk. We derive the small-scale velocity field of the penumbra in the deep photosphere. Superimposed on a radial outflow, we find up- and downflows, which are associated with bright and dark features: The flow in the dark component of the penumbra has a larger inclination angle with respect to the surface normal than the bright component, everywhere in the penumbra. The maximum inclination difference is 8o. In the inner and mid penumbra, bright features (penumbral grains) are associated with an upflow of about 0.6 km s-1. At the outer spot boundary, the flow is inclined downwards predominantly in the dark component ([FORMULA]).

Key words: Sun: photosphere – Sun: sunspots – Sun: magnetic fields


© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001

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