  It is now well established that the quiet Sun contains in total more magnetic
flux than active regions and represents an important reservoir of magnetic
energy. But the nature and evolution of these fields remain largely unknown.
  We investigate the solar-cycle and center-to-limb variations of magnetic-flux
structures at small scales in internetwork regions of the quiet Sun.
  We used Hinode SOT/SP data from the irradiance program between 2008 and 2016.
Maps of the magnetic-flux density are derived from the center-of gravity method
applied to the FeI 630.15 nm and FeI 630.25 nm lines. To correct the maps from
the instrumental smearing, we applied a deconvolution method based on a
principal component analysis of the line profiles and on a Richardson-Lucy
deconvolution of their coefficients. We then performed a spectral analysis of
the spatial fluctuations of the magnetic-flux density in 10'' x 10''
internetwork regions spanning a wide range of latitudes.
  At low and mid latitudes the power spectra do not vary significantly with the
solar cycle. However at solar maximum for one scan in the activity belt showing
an enhanced network, a marginal increase in the power of the magnetic
fluctuations is observed at granular and larger scales in the internetwork. At
high latitudes, we observe variations at granular and larger scales where the
power decreases at solar maximum. At all the latitudes the power of the
magnetic fluctuations at scales smaller than 0.5''remain constant throughout
the solar cycle.
  Our results favor a small-scale dynamo that operates in the internetwork, but
they show that the global dynamo also contributes to the internetwork fields.
