Abstract

We examine data from the Hinode Observing Program 79 (the “HOP 79” irradiance program) as observed using the Hinode Solar Optical Telescope Spectro-Polarimeter for systematic changes in the weakest observable magnetic flux during the period 2008–2013. At moderate latitudes we find no evidence for... Show moreWe examine data from the Hinode Observing Program 79 (the “HOP 79” irradiance program) as observed using the Hinode Solar Optical Telescope Spectro-Polarimeter for systematic changes in the weakest observable magnetic flux during the period 2008–2013. At moderate latitudes we find no evidence for systematic changes as a function of time and solar latitude in either the unsigned line-of-sight flux or in the measures of the transverse flux. However, in the polar regions, changes are apparent in the measure of signed magnetic flux corresponding to reversal of the polarity of the poles, changes that persist even for the weakest observed flux. Also evident in measures of the weakest signed flux are preferences for positive (negative) polarity at mid-north (mid-south) latitudes (20°–60°). Center-limb variations in various measures of the weak flux appear to be independent of the solar cycle. The results are consistent with the operation of a small-scale solar dynamo operating within and just below the solar photosphere, but the measures of the weakest signed flux still contain small signatures of the global solar cycle. Show less