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We analyze recent high resolution photospheric small-scale dynamo simulationsthat were computed with the MURaM radiative MHD code. We focus the analysis onnewly forming downflow lanes in exploding granules since they show how weaklymagnetized regions in the photosphere (center of granules) evolve into stronglymagnetized regions (downflow lanes). We find that newly formed downflow lanesexhibit initially mostly a laminar converging flow that amplifies the verticalmagnetic field embedded in the granule from a few 10 G to field strengthsexceeding 800 G. This results in extended magnetic sheets that have a lengthcomparable to granular scales. Field amplification by turbulent shear happensfirst a few 100 km beneath the visible layers of the photosphere. Shallowrecirculation transports the resulting turbulent field into the photospherewithin minutes, after which the newly formed downflow lane shows a mix ofstrong magnetic sheets and turbulent field components. We stress in particularthe role of shallow and deep recirculation for the organization and strength ofmagnetic field in the photosphere and discuss the photospheric andsub-photospheric energy conversion associated with the small-scale dynamoprocess. While the energy conversion through the Lorentz force depends onlyweakly on the saturation field strength (and therefore deep or shallowrecirculation), it is strongly dependent on the magnetic Prandtl number. Wediscuss the potential of these findings for further constraining small-scaledynamo models through high resolution observations.

Small-scale dynamo simulations: Magnetic field amplification in exploding granules and the role of deep and shallow recirculation