Ba ii 4554 Å speckle imaging as solar Doppler diagnostic
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: email@example.com
Corresponding author: P. Sütterlin, P.Suetterlin@astro.uu.nl
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
© ESO, 2001