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

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Letter to the Editor

Dependence of the photospheric vertical flow characteristics on the granule dimension *

F. Berrilli 1, A. Florio 2, G. Consolini 3, B. Bavassano 3, C. Briand 4, R. Bruno 3, B. Caccin 1, V. Carbone 5, G. Ceppatelli 4, A. Egidi 1, I. Ermolli 2, G. Mainella 3 and E. Pietropaolo 6

1 Dipartimento di Fisica, Università degli Studi di Roma "Tor Vergata", I-00133 Roma, Italy
2 Osservatorio Astronomico di Roma, I-00136 Roma, Italy
3 Istituto di Fisica dello Spazio Interplanetario - CNR, I-00133 Roma, Italy
4 THEMIS, Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife, Spain
5 Dipartimento di Fisica e Istituto Nazionale di Fisica della Materia, Università della Calabria, I-87036 Rende (CS), Italy
6 Dipartimento di Fisica, Università degli Studi dell'Aquila, I-67010 L'Aquila, Italy

Received 8 January 1999 / Accepted 26 February 1999


The first high spectral resolution and white-light images obtained at the THEMIS telescope with the Italian Panoramic Monochromator (IPM), are analyzed to study intensity and velocity fluctuations in the photosphere of the sun. Monochromatic images, in two spectral ranges around 538.03 nm (C I line) and 557.61 nm (Fe I line), are used to characterize the vertical structure of the photosphere. Granulation cells and granules are obtained by segmentation of white-light images using suitable finding algorithms.

We observe the height dependence of velocity vs. intensity fluctuations, and we found a dependence of velocity and intensity on granule dimension. Our results show that granules increase their intensity with dimension in the lower solar photosphere. In the higher photosphere, on the contrary, the intensity decreases with the dimension.

Key words: Sun: photosphere – Sun: granulation – techniques: image processing

* Based on THEMIS/CNRS-INSU/CNR telescope observations

Send offprint requests to: F. Berrilli (berrilli@roma2.infn.it)

© European Southern Observatory (ESO) 1999

Online publication: March 18, 1999