Small-Scale Flux Emergence Observed Using Hinode/SOT

Abstract

The aim of this paper is to determine the flux emergence rate due to small-scale magnetic features in the quiet Sun using high-resolution Hinode SOT NFI data. Small-scale magnetic features are identified in the data using two different feature identification methods (clumping and downhill); then three methods are applied to detect flux emergence events. The distribution of the intranetwork peak emerged fluxes is determined. When combined with previous emergence results, from ephemeral regions to sunspots, the distribution of all fluxes are found to follow a power-law distribution which spans nearly seven orders of magnitude in flux (1016 – 1023 Mx) and 18 orders of magnitude in frequency. The power-law fit to all these data is of the form $$\frac{\mathrm{d}N}{\mathrm{d}\Psi} = \frac{n_0}{\Psi_0}\frac{\Psi}{\Psi _0}^{-2.7},$$ where Ψ0=1016 Mx and is used to predict a global flux emergence rate of ≈ 450 Mx cm−2 day−1 from all features with fluxes of 1016 Mx or more. Since the slope of all emerged fluxes is less than −2, this implies that most of the new flux that is fed into the solar atmosphere is from small-scale emerging events. This suggests that the rate of flux emergence is independent of the solar cycle and is equivalent to a global rate of flux emergence of more than a few times 1025 Mx day−1. The single power-law distribution over all emerged fluxes implies a scale-free dynamo, therefore indicating that a turbulent dynamo may act throughout the convection zone. Moreover, from the slope of the emerging flux distribution the (turbulent?) dynamo producing small-scale features produces considerably more flux than the active-region dynamo at the tachocline.