Magnetic Contamination and Correction in Sodium Dopplergrams

Recently a new version of a sodium double-band magneto-optical filter has been built in order to provide simultaneous Doppler and magnetograms using the same optical path (Cacciani, Moretti, and Rodgers, 1997; Cacciani et al., 1988, 1994). Two observing stations based on this instrument are being installed as part of the French network IRIS. One is already operational in Apple Valley, California, and the other one will be delivered shortly to Tashkent, Uzbekistan. The performance of the instrument is such as to detect the l = 0 mode of solar oscillations from resolved images with a signal-to-noise ratio that has never been achieved before (Cacciani and Moretti, 1994). The magnetic and velocity signals are corrected for the changes that occur in the solar D-line profile in active versus non-active regions. This kind of analysis will be performed by our group in conjunction with parallel analysis of GOLF and IRIS integrated data which use the same sodium lines.