Photospheric flows measured with TRACE II. Network formation

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

Corresponding author: J. M. Krijger, J.M.Krijger@astro.uu.nl

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   (≈ 93 Mm 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  10²² Mx h^-1 with an average flux per region of about 1.1  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.