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

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 8^o. 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 ().

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

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. Observations and data reduction
  • 2.1. Selection of bright and dark component
  • 2.2. Flow angle and flow velocity
  • 2.3. Error analysis
• 3. Results
• 4. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001
helpdesk.link@springer.de