Pair separation of magnetic elements in the quiet Sun

Giannattasio, Fabio; Berrilli, F.; Biferale, Luca; Moro, D. Del; Sbragaglia, Mauro; Rubio, L. R. Bellot; Gošić, Milan; Suárez, D. Orozco

doi:10.1051/0004-6361/201424380

Cited by 25 publications

(14 citation statements)

References 49 publications

(65 reference statements)

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“…Other analogies between the views of Escande & Sattin (2007) and Solomon et al (1994) and our algorithm and the possibility of further extending their results (by applying the pair separation approach of Giannattasio et al 2014b), are at the moment under investigation.…”

Section: Discussionmentioning

confidence: 89%

Super-diffusion versus competitive advection: a simulation

Moro

Giannattasio

Berrilli

et al. 2015

A&A

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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.

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Section: Discussionmentioning

confidence: 89%

Super-diffusion versus competitive advection: a simulation

Moro

Giannattasio

Berrilli

et al. 2015

A&A

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“…Giannattasio et al (2013) studied the long-duration transport by tracking the turbulent convective flows of a large number of magnetic elements over 25 hr in the field of view of an entire supergranule cell and identified a double-regime behaviour in the displacement spectrum of the magnetic elements: superdiffusive in the whole field of view up to granular spatial scales (∼ 1.5 Mm) and slightly diffusive up to supergranular spatial scales (∼30∼35 Mm). Giannattasio et al (2014a) investigated the separation spectrum for different values of the initial pair separation of magnetic elements for an entire supergranule and found out that the rate of pair separation depends on the spatial scale under consideration. Giannattasio et al (2014b) found that the amplitude of horizontal velocity field is small in the centre of the supergranular cell (∼10 m/s), and increases toward the supergranular boundaries reaching a maximum (∼600 m/s) at about half the radius.…”

Section: Introductionmentioning

confidence: 99%

Supergranular turbulence in the quiet Sun: Lagrangian coherent structures

Chian

Silva²,

Rempel

et al. 2019

Monthly Notices of the Royal Astronomical Society

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ABSTRACT The quiet Sun exhibits a wealth of magnetic activities that are fundamental for our understanding of solar magnetism. The magnetic fields in the quiet Sun are observed to evolve coherently, interacting with each other to form prominent structures as they are advected by photospheric flows. The aim of this paper is to study supergranular turbulence by detecting Lagrangian coherent structures (LCS) based on the horizontal velocity fields derived from Hinode intensity images at disc centre of the quiet Sun on 2010 November 2. LCS act as transport barriers and are responsible for attracting/repelling the fluid elements and swirling motions in a finite time. Repelling/attracting LCS are found by computing the forward/backward finite-time Lyapunov exponent (FTLE), and vortices are found by the Lagrangian-averaged vorticity deviation method. We show that the Lagrangian centres and boundaries of supergranular cells are given by the local maximum of the forward and backward FTLE, respectively. The attracting LCS expose the location of the sinks of photospheric flows at supergranular junctions, whereas the repelling LCS interconnect the Lagrangian centres of neighbouring supergranular cells. Lagrangian transport barriers are found within a supergranular cell and from one cell to other cells, which play a key role in the dynamics of internetwork and network magnetic elements. Such barriers favour the formation of vortices in supergranular junctions. In particular, we show that the magnetic field distribution in the quiet Sun is determined by the combined action of attracting/repelling LCS and vortices.

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“…The solar turbulent convection covers a wide range of spatial and temporal scales, and it is usually described in terms of different phenomena; i.e., granulation, mesogranulation and supergranulation. Nonetheless, it exhibits properties that continuously extend over the different scales, suggesting that solar convection requires a comprehensive analysis for its understanding (see, e.g., [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]). The granular scale is the spatial scale where most of the energy carried by the convection is delivered in the photosphere.…”

Section: Introductionmentioning

confidence: 99%

Testing the Steady-State Fluctuation Relation in the Solar Photospheric Convection

Viavattene

Consolini

Giovannelli

et al. 2020

Entropy

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The turbulent thermal convection on the Sun is an example of an irreversible non-equilibrium phenomenon in a quasi-steady state characterized by a continuous entropy production rate. Here, the statistical features of a proxy of the local entropy production rate, in solar quiet regions at different timescales, are investigated and compared with the symmetry conjecture of the steady-state fluctuation theorem by Gallavotti and Cohen. Our results show that solar turbulent convection satisfies the symmetries predicted by the fluctuation relation of the Gallavotti and Cohen theorem at a local level.

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Pair separation of magnetic elements in the quiet Sun

Cited by 25 publications

References 49 publications

Super-diffusion versus competitive advection: a simulation

Super-diffusion versus competitive advection: a simulation

Supergranular turbulence in the quiet Sun: Lagrangian coherent structures

Testing the Steady-State Fluctuation Relation in the Solar Photospheric Convection

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