  Using both wavelet and Fourier analysis, a study has been undertaken of the
changes in the quasi-periodic variations in solar photospheric fields in the
build-up to one of the deepest solar minima experienced in the past 100 years.
This unusual and deep solar minimum occurred between solar cycles 23 and 24.
The study, carried out using ground based synoptic magnetograms spanning the
period 1975.14 to 2009.86, covered solar cycles 21, 22 and 23. A hemispheric
asymmetry in periodicities of the photospheric fields was seen only at
latitudes above $\pm45{^{\circ}}$ when the data was divided, based on a wavelet
analysis, into two parts: one prior to 1996 and the other after 1996.
Furthermore, the hemispheric asymmetry was observed to be confined to the
latitude range 45${^{\circ}}$ to 60${^{\circ}}$. This can be attributed to the
variations in polar surges that primarily depend on both the emergence of
surface magnetic flux and varying solar surface flows. The observed asymmetry
when coupled with the fact that both solar fields above $\pm45{^{\circ}}$ and
micro-turbulence levels in the inner-heliosphere have been decreasing since the
early to mid nineties (Janardhan et al., 2011) suggests that around this time
active changes occurred in the solar dynamo that governs the underlying basic
processes in the sun. These changes in turn probably initiated the build-up to
the very deep solar minimum at the end of the cycle 23. The decline in fields
above $\pm45{^{\circ}}$ for well over a solar cycle, would imply that weak
polar fields have been generated in the past two successive solar cycles
\textit{viz.} cycles 22 and 23. A continuation of this declining trend beyond
22 years, if it occurs, will have serious implications on our current
understanding of the solar dynamo.
