Spatial Nonlocality of the Small-Scale Solar Dynamo

Abstract

We explore the nature of the small-scale solar dynamo by tracking magnetic features. We investigate two previously explored categories of the small-scale solar dynamo: shallow and deep. Recent modeling work on the shallow dynamo has produced a number of scenarios for how a strong network concentration can influence the formation and polarity of nearby small-scale magnetic features. These scenarios have measurable signatures, for which we test using magnetograms from the Narrowband Filter Imager (NFI) on board Hinode. We find no statistical tendency for newly formed magnetic features to cluster around or away from network concentrations, nor do we find any statistical relationship between their polarities. We conclude that there is no shallow or "surface" dynamo on the spatial scales observable by Hinode/NFI. In light of these results, we offer a scenario in which the subsurface field in a deep solar dynamo is stretched and distorted via turbulence, allowing the small-scale field to emerge at random locations on the photosphere.

Small-scale Dynamo Simulations: Magnetic Field Amplification in Exploding Granules and the Role of Deep and Shallow Recirculation

“…Observations suggest that small-scale magnetic field in the solar photosphere is mostly independent from the strength of nearby network field (Ishikawa & Tsuneta 2009;Lites 2011;Lamb et al 2014) as well as independent of the solar cycle (Buehler et al 2013;Lites et al 2014). This supports the view that the origin of small-scale magnetism is due to a small-scale dynamo that operates independently from the large-scale dynamo responsible for the solar cycle.…”

Undetected Minority-Polarity Flux as the Missing Link in Coronal Heating

“…The origin of bipoles with total fluxes 10 20 Mx, including in particular ERs, is often attributed to a poorly understood small-scale dynamo, in which turbulent convection acts to shred the larger-scale fields originating from the main, rotationally driven dynamo associated with sunspots and ARs (see, e.g., Cattaneo, 1999;Cattaneo, Emonet, and Weiss, 2003;Guglielmino et al, 2012). Based on the lack of correlation between the spatial distributions of network concentrations and small-scale fields, Lamb, Howard, and DeForest (2014) suggested that the stretching and shredding occur deep in the convection zone rather than near the solar surface. To our knowledge, however, none of the existing models predicts the emergence of small-scale fields within AR plages.…”

The best of both worlds: Using automatic detection and limited human supervision to create a homogenous magnetic catalog spanning four solar cycles

“…While this is sufficient to seed solar dynamo and surface flux transport models, as well as to characterize the large scale statistical properties of BMRs and their dependence of solar activity, there is immense value in building catalogs that take advantage of full instrumental cadence and scale. The reason is that such a catalog will enable a wide array of statistical analyses that can shed light in the scaling and origin of surface magnetism [7]- [10], the nature of observable dynamo action [10], [11], dependence of surface magnetism on solar activity [12], [13], and characterization of the solar extended cycle [14], [15], among many other examples.…”

“…Starting development in 2001, SWAMIS [16] has evolved to be a truly multi-scale detection algorithm that has been used to study flux balance in solar surface magnetism [17], [18], flux distribution of magnetic elements [9], dissipation of surface magnetic elements [19], and locality of surface dynamo action [11].…”