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Issue A&A
Volume 403, Number 2, May IV 2003
Page(s) 715 - 723
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20030387



A&A 403, 715-723 (2003)
DOI: 10.1051/0004-6361:20030387

Photospheric flows measured with TRACE II. Network formation

J. M. Krijger1 and T. Roudier2

1  Sterrekundig Instituut, Postbus 80 000, 3508 TA Utrecht, The Netherlands
2  Laboratoire d'Astrophysique de Toulouse, Observatoire Midi-Pyrénées, 14 Avenue E. Belin, 31400 Toulouse, France
    e-mail: roudier@bagn.obs-mip.fr

(Received 26 July 2002 / Accepted 7 March 2003 )

Abstract
We analyse a 7 d (167 h) sequence of TRACE white-light images with 1´´ angular resolution taken at 1 min cadence. The TRACE resolution and the fast cadence allows us to produce maps of the horizontal flow fields with high angular (1´´) and temporal resolution (5 min). The field of view of $128\arcsec$  $\times$ $128\arcsec$ ( $\approx$ 93 Mm $\times$ 93 Mm) covers approximately an area of  10 to 30 supergranules. This area was followed during solar rotation. Magnetic flux was artificially inserted into the successive flow maps in the form of ephemeral regions with positive and negative polarity. The emergence rate of 2  $\times$ 1022 Mx h -1 with an average flux per region of about 1.1  $\times$ 1019 Mx produces a good reproduction of the chromospheric network as observed in images taken simultaneously at 1600 Å. In addition, we show that the quiet network can be maintained only if field elements of both polarities are inserted into the flow fields. Our analysis suggests that the network is fully replenished on a time scale of a day and the lifetimes of the magnetic elements are of a similar duration.


Key words: Sun: photosphere -- Sun: chromosphere -- Sun: granulation

Offprint request: J. M. Krijger, J.M.Krijger@astro.uu.nl




© ESO 2003

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