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Astron. Astrophys. 344, L29-L32 (1999)

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1. Introduction

Small scale motions on the surface of the sun, known as solar granulation, and due to the overshoot of convective elements into the photosphere, yield a pattern of bright granules surrounded by dark intergranular lanes. These motions overturn in about 10 minutes and are roughly 1500 km across. The analysis of the penetration of the granulation into the solar photosphere, and in particular the height dependence of intensity and velocity fields, give us insights about the role of the convective overshoot, the structure of velocity patterns and the generation of 5-minutes oscillation (cf. Nesis et al. 1996).

Moreover, the geometrical approach in the definition of the properties of granules and granular cells (Roudier & Muller 1986, Title et al. 1989, Noever 1994, Hirzberger et al. 1997, Schrijver et al. 1997) and the study of small-scale features (Rast 1995, Roudier et al. 1997, Hoekzema et al. 1998), would be extremely rewarding for the understanding of the physical processes taking place in this region, and to check hydrodynamic models of solar granulation (cf. Gadun & Pikalov 1996, Stein & Nordlund 1998).

Spectroscopy allows us to investigate different layers of the solar photosphere, and in particular two-dimensional techniques can improve the approach to the definition of the dynamics of this atmospheric region.

In this work we analyze intensity and velocity properties of the solar photosphere in relation to continuum structures. We extract from white-light (WL) images the granules and the granulation cells (Florio & Berrilli 1998) to investigate co-located intensity and velocity fluctuations in the lower and higher photosphere.

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© European Southern Observatory (ESO) 1999

Online publication: March 18, 1999