  The solar mean magnetic field (SMMF) is referred to as the disc-averaged
line-of-sight (LOS) magnetic field that also reflects the polarity imbalance of
the magnetic field on the Sun. The origin of the SMMF has been debated over the
past few decades, with one school of thought suggesting that the contribution
to the SMMF is mostly due to the large scale magnetic field structure, also
termed as the background magnetic field, whereas other and more recent studies
have indicated that active regions have a major contribution to the observed
SMMF. In this paper, we re-investigate the issue of the origin of the SMMF by
decomposing the solar disk into plages, networks, sunspots and background
regions, thereby calculating the variation in the observed SMMF due to each of
these features. We have used full disk images from SDO/{\it AIA} recorded at
1600~\AA\, for earmarking plages, networks and background regions and
4500~\AA\, images for separating the sunspots. The LOS fields corresponding to
each of these regions are estimated from the co-temporal SDO/{\it HMI} full
disk magnetograms. The temporal variation of the SMMF shows a near one-to-one
correspondence with that of the background field regions suggesting that they
constitute the major component of the observed SMMF. A linear regression
analysis based on the coefficient of determination shows that the background
field dominates, and accounts for 89\% of the variation in the SMMF whereas the
magnetic field from the other features accounts for the rest 11\%.
