Is There Observational Evidence Indicating a Small-Scale Solar Dynamo?

摘要

Observations from the Hinode/SOT spectro-polarimeter are examined with the aim of identifying diagnostics for the presence (or absence) of a self-sustained small-scale turbulent dynamo in the upper solar convection zone. We examine 45 Hinode data sets obtained during 2007. We find much smaller net flux imbalance within regions of the quiet Sun having very weak flux compared to the imbalance averaged over each data set. Further, there is no correlation of the average net unsigned flux of regions having very weak flux relative to the average unsigned flux of the entire region. If internetwork fields were to arise from dispersal of flux from active regions, one would expect both measures to show significant correlation, so this analysis strongly supports the small-scale dynamo scenario. We also find that the average of the longitudinal apparent flux density increases slightly toward the limb for the very weakest observed flux elements. This behavior is likely the result of the dominance of horizontal fields higher in the photosphere. From data with very high signal-to-noise ratio, the distribution of magnetic field strength indicates that the magnetic energy of the quiet Sun is dominated by the small fraction of field elements having kG strengths. These strong-field elements are responsible for most of the imbalance of magnetic flux measured in each region, so it is suggested that they arise primarily from dispersal of flux from active regions, not from a small-scale dynamo.