Volume 576, April 2015
|Number of page(s)||6|
|Published online||26 March 2015|
Super-diffusion versus competitive advection: a simulation
Dipartimento di FisicaUniversità degli Studi di Roma “Tor
via della Ricerca Scientifica 1,
2 INAF–Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere 10, 00133 Roma, Italy
3 Dipartimento di Fisica, Università della Calabria, Ponte P. Bucci 31/C, 87036 Rende, Italy
4 CNISM, Unità di Ricerca di Cosenza, Ponte P. Bucci 31/C, 87036 Rende, Italy
5 Instituto de Astrofísica de Andalucía (CSIC), Apdo. 3004, 18080 Granada, Spain
Received: 17 July 2014
Accepted: 22 January 2015
Context. Magnetic element tracking is often used to study the transport and diffusion of the magnetic field on the solar photosphere. From the analysis of the displacement spectrum of these tracers, it has recently been agreed that a regime of super-diffusivity dominates the solar surface. Quite habitually this result is discussed in the framework of fully developed turbulence.
Aims. However, the debate whether the super-diffusivity is generated by a turbulent dispersion process, by the advection due to the convective pattern, or even by another process is still open, as is the question of the amount of diffusivity at the scales relevant to the local dynamo process.
Methods. To understand how such peculiar diffusion in the solar atmosphere takes place, we compared the results from two different data sets (ground-based and space-borne) and developed a simulation of passive tracers advection by the deformation of a Voronoi network.
Results. The displacement spectra of the magnetic elements obtained by the data sets are consistent in retrieving a super-diffusive regime for the solar photosphere, but the simulation also shows a super-diffusive displacement spectrum: its competitive advection process can reproduce the signature of super-diffusion.
Conclusions. Therefore, it is not necessary to hypothesize a totally developed turbulence regime to explain the motion of the magnetic elements on the solar surface.
Key words: convection / hydrodynamics / turbulence / Sun: photosphere
© ESO, 2015
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