Mesoscale dynamics on the Sun's surface from HINODE observations

Abstract

Aims: The interactions of velocity scales on the Sun's surface, from granulation to supergranulation are still not understood, nor are their interaction with magnetic fields. We thus aim at giving a better description of dynamics in the mesoscale range which lies between the two scales mentioned above. Method: We analyse a 48h high-resolution time sequence of the quiet Sun photosphere at the disk center obtained with the Solar Optical Telescope onboard Hinode. The observations, which have a field of view of 100 \arcsec$\times$ 100 \arcsec, typically contain four supergranules. We monitor in detail the motion and evolution of granules as well as those of the radial magnetic field. Results: This analysis allows us to better characterize Trees of Fragmenting Granules issued from repeated fragmentation of granules, especially their lifetime statistics. Using floating corks advected by measured velocity fields, we show their crucial role in the advection of the magnetic field and in the build up of the network. Finally, thanks to the long duration of the time series, we estimate that the turbulent diffusion coefficient induced by horizontal motion is approximately $430{\mathrm{km}}^2{\mathrm{s}}^{-1}$. Conclusions: These results demonstrate that the long living families contribute to the formation of the magnetic network and suggest that supergranulation could be an emergent length scale building up as small magnetic elements are advected and concentrated by TFG flows. Our estimate for the magnetic diffusion associated with this horizontal motion might provide a useful input for mean-field dynamo models.

to appear in A&A - 8 pages, 13 figures (degraded quality) - Full resolution version available @ http://www.ast.obs-mip.fr/users/rincon/hinode_roudier_aa09.pdf

References in corpus (7)

• Astrophysical magnetic fields and nonlinear dynamo theory
• Solar supergranulation as a wavelike phenomenon
• Inter-Network magnetic fields observed with sub-arcsec resolution
• Are granules good tracers of solar surface velocity fields?
• Local helioseismology and correlation tracking analysis of surface structures in realistic simulations of solar convection
• Solar supergranulation revealed by granule tracking
• Mesoscale flows in large aspect ratio simulations of turbulent compressible convection

Cited by in corpus (14)

• Predicting the Sun's Polar Magnetic Fields with a Surface Flux Transport Model
• Effects of Meridional Flow Variations on Solar Cycles 23 and 24
• Characteristic scales of magnetic switchback patches near the Sun and their possible association with solar supergranulation and granulation
• Migration of Ca II H bright points in the internetwork
• Mesogranulation and the solar surface magnetic field distribution
• Detection of coherent structures in photospheric turbulent flows
• Supergranulation and multiscale flows in the solar photosphere: Global observations vs. a theory of anisotropic turbulent convection
• Relation between trees of fragmenting granules and supergranulation evolution
• Modelling solar irradiance variability on time scales from minutes to months
• Synchronized Observations of Bright Points from the Solar Photosphere to Corona
• Link between trees of fragmenting granules and deep downflows in MHD simulation
• Texture of average solar photospheric flows and the donut-like pattern
• Observational characterisation of large-scale transport and horizontal turbulent diffusivity in the quiet Sun
• MHD simulations of the solar photosphere