EDP Sciences
Free access
Volume 428, Number 2, December III 2004
Page(s) 613 - 628
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20040436

A&A 428, 613-628 (2004)
DOI: 10.1051/0004-6361:20040436

Solar magnetic elements at 0 $\farcs$1 resolution

General appearance and magnetic structure
T. E. Berger1, L. H. M. Rouppe van der Voort2, M. G. Löfdahl3, M. Carlsson2, 4, A. Fossum2, V. H. Hansteen2, 4, E. Marthinussen2, A. Title1 and G. Scharmer3

1  Lockheed Martin Solar and Astrophysics Lab, 3251 Hanover St., Palo Alto, California 94304, USA
    e-mail: berger@lmsal.com
2  Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
3  The Institute for Solar Physics of the Royal Swedish Academy of Sciences, Alba Nova University Center, 10691 Stockholm, Sweden
4  Center of Mathematics for Applications, University of Oslo, PO Box 1053 Blindern, 0316 Oslo, Norway

(Received 13 March 2004 / Accepted 27 August 2004 )

New observations of solar magnetic elements in a remnant active region plage near disk center are presented. The observations were obtained at the recently commissioned Swedish 1-m Solar Telescope on La Palma. We examine a single 430.5 nm G-band filtergram that resolves ~70 km (0 $\farcs$1) structures and find new forms of magnetic structures in this particular region. A cotemporal $\ion{Ca}{ii}$ H-line image is used to examine the low-chromosphere of network elements. A cotemporal $\ion{Fe}{i}$ 630.25 nm magnetogram that resolves structures as small as 120 km (0 $\farcs$18) FWHM with a flux sensitivity of approximately 130 Mx cm -2 quantifies the magnetic structure of the region. A $\ion{Ni}{i}$ 676.8 nm Dopplergram establishes relative velocity patterns associated with the network features with an accuracy of about 300 m s -1. We find that magnetic flux in this region as seen in both the magnetogram and the G-band image is typically structured into larger, amorphous, "ribbons" which are not resolved into individual flux tubes. The measured magnetic flux density in the ribbon structures ranges from 300 to 1500 Mx cm -2, the higher values occurring at localized concentrations embedded within the ribbons. The Dopplergram indicates relative downflows associated with all magnetic elements with some indication that higher downflows occur adjacent to the peak magnetic flux location. The mean absolute magnetic flux density of the remnant plage network is about 130 Mx cm -2; in the lowest flux regions of the field-of-view, the mean absolute flux density is approximately 60 Mx cm -2. Within these quiet regions we do not find evidence of pervasive kilo-gauss strength magnetic elements as seen in recent high resolution internetwork studies. In general, the observations confirm recent 3-dimensional numerical simulations which show that the magnetic field in high-density regions such as plage is concentrated in complex structures that are not generally composed of discrete magnetic flux tubes.

Key words: Sun: magnetic fields -- convection

© ESO 2004