Small-scale flow field in a sunspot penumbra

We have measured Velocity maps of a round sunspot near the center of the so lar disk. We derive the small-scale velocity field of the penumbra in the d eep photosphere. Superimposed on a radial outflow, we find up- and downflow s, 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 t he surface normal than the bright component, everywhere in the penumbra. Th e maximum inclination difference is 8 degrees. In the inner and mid penumbr a, bright features (penumbral grains) are associated with an upflow of abou t 0.6 km s(-1). At the outer spot boundary, the flow is inclined downwards predominantly in the dark component (-7 degrees).