EDP Sciences
Free access
Volume 378, Number 1, October IV 2001
Page(s) 251 - 256
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20011176

A&A 378, 251-256 (2001)
DOI: 10.1051/0004-6361:20011176

Ba II 4554 Å speckle imaging as solar Doppler diagnostic

P. Sütterlin1, R. J. Rutten1 and V. I. Skomorovsky2

1  Sterrekundig Instituut Utrecht, Postbus 80 000, 3508 TA Utrecht, The Netherlands
    e-mail: R.J.Rutten@astro.uu.nl
2  Institute of Solar-Terrestrial Physics, 664033 Irkutsk, PO Box 4026, Russia
    e-mail: skoal@iszf.irk.ru

(Received 12 July 2001 / Accepted 20 August 2001)

We present observations testing the Dopplergram capability of a narrow-band (80 mÅ) Lyot filter imaging the solar surface in the wings of the Ba II 4554 Å resonance line in combination with speckle reconstruction to obtain high angular resolution. The Ba II line is found to be an excellent tool for high-resolution Doppler mapping thanks to opacity insensitivity to temperature variations and line-width insensitivity to thermal broadening. The resulting Dopplergrams show concentrated downflows of 1.2-2.2 kms-1 in intergranular lanes that probably mark magnetic fluxtubes. Two-wavelength profile sampling is found to suffice for high-resolution Dopplergram construction. The filter will be installed as part of a multi-wavelength speckle imaging system on the new Dutch Open Telescope.

Key words: Sun: atmosphere -- Sun: photosphere -- Sun: faculae, plages -- techniques: image processing -- instrumentation: miscellaneous

Offprint request: P. Sütterlin, P.Suetterlin@astro.uu.nl

© ESO 2001