  The Solar Mean Magnetic Field (SMMF) is the mean value of the line of sight
(LOS) component of the solar vector magnetic field averaged over the visible
hemisphere of the Sun. So far, the studies on SMMF have mostly been confined to
the magnetic field measurements at the photosphere. In this study, we calculate
and analyse the SMMF using magnetic field measurements at the chromosphere, in
conjunction with that of photospheric measurements. For this purpose, we have
used full disk LOS magnetograms derived from spectropolarimetric observations
carried out in Fe I 630.15 nm and Ca II 854.2 nm by the Synoptic Optical Long
term Investigations of the Sun (SOLIS)/Vector Spectromagnetograph (VSM)
instrument during 2010 to 2017. It is found from this study that the SMMF at
the chromosphere is weaker by a factor of 0.60 compared to the SMMF at the
upper photosphere. The correlation analysis between them gives a Pearson
correlation coefficient of 0.80. The similarity and reduced intensity of the
chromospheric SMMF with respect to the photospheric SMMF corroborate the idea
that it is the source of the Interplanetary Magnetic Field (IMF).
