SOLIS-VSM Longitudinal Magnetogram Calibration


The VSM (Vector SpectroMagnetograph) instrument started recording daily full-disk magnetograms during August, 2003 at a temporary site in Tucson, Arizona. Along with the other instruments that constitute the SOLIS (Synoptic Optical Long-term Investigations of the Sun) project, the VSM will be relocated to Kitt Peak in April, 2004. The VSM instrument provides a unique record of solar full-disk vector magnetograms along with the high sensitivity photospheric and chromospheric longitudinal magnetograms. In addition, the VSM takes daily full-disk He I 1083 nm equivalent width observations. These parameter-grams are constructed from individual scans in declination of the projected solar image on the entrance slit with a relatively large field angle of over a half of a degree in the spectrograph. The calibration of the VSM longitudinal magnetic observations is reviewed, along with a comparison between the VSM mean field, sun-as-a-star, measurements with those by the Wilcox Solar Observatory. In addition, the making of synoptic maps derived from the VSM magnetograms is discussed, including the filling of data gaps in polar regions and the use of accompanying weight maps. VSM magnetograms and synoptic maps are available via the Internet at: This research was supported in part by the Office of Naval Research Grant N00014-91-J-1040. The National Solar Observatory is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation.

American Astronomical Society Meeting Abstracts #204