Photospheric supergranular flows and magnetic flux emergence

Stangalini, M.

doi:10.1051/0004-6361/201322831

Cited by 22 publications

(22 citation statements)

References 38 publications

(57 reference statements)

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“…Moreover, the study of the dynamics of the magnetic elements on the solar photosphere is of particular interest in astrophysics, since it could also provide constraints on a) the characteristic spatiotemporal scales of the emergence and diffusion processes of the magnetic field (e.g. Orozco Stangalini 2014); b) the rates of interaction between the magnetic elements themselves, which can cause magnetic reconnections and subsequent micro-flaring events: a plausible mechanism for the heating of the upper solar atmosphere (as in the model of Viticchié et al 2006).…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

Super-diffusion versus competitive advection: a simulation

Moro

Giannattasio

Berrilli

et al. 2015

A&A

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“…This possibility appears even more attractive since high resolution observations have shown that small magnetic elements with diameters ∼100−150 km cover a significant fraction of the solar photosphere (Lagg et al 2010;Bonet et al 2012), although it has been shown that magnetic flux emergence is not homogeneous (Stangalini 2014).…”

Section: Introductionmentioning

confidence: 99%

Observational evidence for buffeting-induced kink waves in solar magnetic elements

Stangalini

Consolini

Berrilli

et al. 2014

A&A

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The role of diffuse photospheric magnetic elements in the energy budget of the upper layers of the Sun's atmosphere has been the recent subject of many studies. This was made possible by the availability of high temporal and spatial resolution observations of the solar photosphere, allowing large numbers of magnetic elements to be tracked to study their dynamics. In this work we exploit a long temporal series of seeing-free magnetograms of the solar photosphere to study the effect of the turbulent convection on the excitation of kink oscillations in magnetic elements. We make use of the empirical mode decomposition technique in order to study the transverse oscillations of several magnetic flux tubes. This technique permits analysis of non-stationary time series like those associated to the horizontal velocities of these flux tubes, which are continuously advected and dispersed by granular flows. Our primary findings reveal the excitation of low frequency modes of kink oscillations, which are subharmonics of a fundamental mode with a 7.6 ± 0.2 min periodicity. These results constitute observational proof of the excitation of kink waves by the buffeting of the convection cells in the solar photosphere, and they are discussed in light of their possible role in the energy budget of the upper Sun's atmosphere.

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“…32 This code was originally written for the identification and tracking of small-scale magnetic elements in the solar photosphere; [33][34][35] a task conceptually similar to that of the analysis of AO residual faint speckles in SHARK forerunner data. 36,37 In short, the code identifies and tracks, through sequential images, small-scale features that are above a user-specified threshold (4σ in our case), where σ is the standard deviation of the signal (intensity) computed in a dark region in the upper left corner of the image and covering at least an area of n pixels (where n ¼ 16 in our case). This implies that only structures with a size of the order of the PSF are identified and tracked, thus ruling out the possibility of including noise features.…”

Section: Speckle Lifetime Statisticsmentioning

confidence: 99%

Speckle statistics in adaptive optics images at visible wavelengths

Stangalini

Pedichini

Ambrosino

et al. 2016

Adaptive Optics Systems V

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Abstract. Residual speckles in adaptive optics (AO) images represent a well-known limitation on the achievement of the contrast needed for faint source detection. Speckles in AO imagery can be the result of either residual atmospheric aberrations, not corrected by the AO, or slowly evolving aberrations induced by the optical system. We take advantage of the high temporal cadence (1 ms) of the data acquired by the System for Coronagraphy with High-order Adaptive Optics from R to K bands-VIS forerunner experiment at the Large Binocular Telescope to characterize the AO residual speckles at visible wavelengths. An accurate knowledge of the speckle pattern and its dynamics is of paramount importance for the application of methods aimed at their mitigation. By means of both an automatic identification software and information theory, we study the main statistical properties of AO residuals and their dynamics. We therefore provide a speckle characterization that can be incorporated into numerical simulations to increase their realism and to optimize the performances of both real-time and postprocessing techniques aimed at the reduction of the speckle noise.

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Photospheric supergranular flows and magnetic flux emergence

Cited by 22 publications

References 38 publications

Super-diffusion versus competitive advection: a simulation

Super-diffusion versus competitive advection: a simulation

Observational evidence for buffeting-induced kink waves in solar magnetic elements

Speckle statistics in adaptive optics images at visible wavelengths

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