  The extended minimum of Solar Cycle 23, the extremely quiet solar-wind
conditions prevailing, and the mini-maximum of Solar Cycle 24 drew global
attention and many authors have since attempted to predict the amplitude of the
upcoming Solar Cycle 25, which is predicted to be the third successive weak
cycle; it is a unique opportunity to probe the Sun during such quiet periods.
Earlier work has established a steady decline, over two decades, in solar
photospheric fields at latitudes above $45^{\circ}$ and a similar decline in
solar-wind micro-turbulence levels as measured by interplanetary scintillation
(IPS) observations. However, the relation between the photospheric magnetic
fields and those in the low corona/solar-wind are not straightforward.
Therefore, in the present article, we have used potential-field source-surface
(PFSS) extrapolations to deduce global magnetic-fields using synoptic
magnetograms observed with National Solar Observatory (NSO), Kitt Peak, USA
(NSO/KP) and Solar Optical Long-term Investigation of the Sun (NSO/SOLIS)
instruments during 1975-2018. Furthermore, we have measured the normalized
scintillation index [m] using the IPS observations carried out at the Institute
of Space Earth Environment Research (ISEE), Japan during 1983-2017. From these
observations, we have found that, since the mid-1990s, the magnetic-field over
different latitudes at 2.5 $\rm R_{\odot}$ and 10 $\rm R_{\odot}$(extrapolated
using PFSS method) has decreased by $\approx 11.3-22.2 \%$. In phase with the
declining magnetic-fields, the quantity m also declined by $\approx 23.6 \%$.
These observations emphasize the inter-relationship between the global
magnetic-field and various turbulence parameters in the solar corona and solar
wind.
