The Longitudinal Solar Magnetic Field Measured by SOLIS

The SOLIS (Synoptic Optical Long-term Investigations of the Sun) Vector SpectroMagnetograph (VSM) instrument operating at the National Solar Observatory at Kitt Peak (Arizona) measures the full-disk longitudinal solar magnetic field in the neutral iron spectral lines at 630.15-630.25 nm (photosphere) and ionized calcium spectral line at 854.2 nm (lower chromosphere). Over the past two years a considerable effort has been made to improve the quality of the computed magnetograms. Major modifications to the original data reduction pipeline include a new determination of the instrumental magnetic bias and an improved calibration of the computed solar magnetic flux density. As a result of these changes SOLIS-VSM is now able to provide, among other products, more reliable values of the full-disk mean magnetic flux measured in the photosphere and low chromosphere. In addition, these improvements open the possibility to extend the current SOLIS-VSM catalog with new products of interest to the solar and heliospheric communities. We describe some of these changes and their impact on the quality of the derived SOLIS-VSM data.