  We analysed line-of-sight magnetic fields and magnetic power spectra of an
undisturbed photosphere using magnetograms acquired by the Helioseismic and
Magnetic Imager (HMI) on-board the Solar Dynamic Observatory (SDO) and the Near
InfraRed Imaging Spectrapolarimeter (NIRIS) operating at the Goode Solar
Telescope (GST) of the Big Bear Solar Observatory. In the NIRIS data revealed
the presence of thin flux tubes of 200-400~km in diameter and of field strength
of 1000-2000~G. The HMI power spectra determined for a coronal hole, a quiet
sun and a plage areas exhibit the same spectral index of -1 on a broad range of
spatial scales from 10-20~Mm down to 2.4~Mm. This implies that the same
mechanism(s) of magnetic field generation operate everywhere in the undisturbed
photosphere. The most plausible one is the local turbulent dynamo. When
compared to the HMI spectra, the -1.2 slope of the NIRIS spectrum appears to be
more extended into the short spatial range until the cutoff at 0.8-0.9~Mm,
after which it continues with a steeper slope of -2.2. Comparison of the
observed and Kolmogorov-type spectra allowed us to infer that the Kolmogorov
turbulent cascade cannot account for more than 35\% of the total magnetic
energy observed in the scale range of 3.5-0.3~Mm. The energy excess can be
attributed to other mechanisms of field generation such as the local turbulent
dynamo and magnetic super-diffusivity observed in an undisturbed photosphere
that can slow down the rate of the Kolmogorov cascade leading to a shallower
resulting spectrum.
