June 24, 2021

Solar and Space Physics UNIToV

Gruppo di Fisica Solare e Spaziale Università di Roma Tor Vergata

Super-diffusion vs Competitive Advection

From Giannatasio et al. Astrophys.J. 770 (2013) L36 arXiv:1305.4006
The image shows a saturated magnetogram of the solar Photosphere. Overlaid, some of the tracks of magnetic bright points, used to compute their Average Displacement Spectrum.

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 been recently agreed that a regime of super-diffusivity dominates the solar surface. Quite habitually, this result has been analyzed in the framework of fully developed turbulence.
But the debate whether this is an effect from turbulence or from the convective pattern is still open, as is the question about the amount of diffusivity at the scales relevant to the local dynamo process.

To understand how such peculiar diffusion in the solar atmosphere takes places, we compared the results from two different data-sets (ground-based and space-borne) and developed a simulation of passive tracers advection. The displacement spectra of the magnetic elements obtained by the data-set are consistent in retrieving a super-diffusive regime for the solar photosphere. When analyzed with the same approach as the real data-sets, the simulation also showed a super-diffusive displacement spectrum.

 

More at: www.aanda.org/articles/aa/pdf/2015/04/aa24624-14.pdf