Supergranulation and multiscale flows in the solar photosphere

Rincon, F.; Roudier, T.; Schekochihin, A. A.; Rieutord, M.

doi:10.1051/0004-6361/201629747

Cited by 33 publications

(43 citation statements)

References 47 publications

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“…They were used in the linear extrapolation of the magnetic field to study the structures of the potential magnetic field components. SDO/HMI intensitygrams and dopplergrams: For the day of the eruption, we tracked the granules visible in the HMI Intensitygrams to obtain a high-resolution high-cadence horizontal velocity field utilising coherent structure tracking (CST; Rieutord et al 2007;Rincon et al 2017). The CST velocities are complemented by HMI dopplergrams to form full velocity vectors.…”

Section: Analysed Datasetsmentioning

confidence: 99%

Evolution of photospheric flows under an erupting filament in the quiet-Sun region

Wollmann

Švanda

Korda

et al. 2020

A&A

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Context. We studied the dynamics of the solar atmosphere in the region of a large quiet-Sun filament, which erupted on 21 October 2010. The filament eruption started at its northern end and disappeared from the Hα line-core filtergrams line within a few hours. The very fast motions of the northern leg were recorded in ultraviolet light by the Atmospheric Imaging Assembly (AIA) imager. Aims. We aim to study a wide range of available datasets describing the dynamics of the solar atmosphere for five days around the filament eruption. This interval covers three days of the filament evolution, one day before the filament growth and one day after the eruption. We search for possible triggers that lead to the eruption of the filament. Methods. The surface velocity field in the region of the filament were measured by means of time-distance helioseismology and coherent structure tracking. The apparent velocities in the higher atmosphere were estimated by tracking the features in the 30.4 nm AIA observations. To capture the evolution of the magnetic field, we extrapolated the photospheric line-of-sight magnetograms and also computed the decay index of the magnetic field. Results. We found that photospheric velocity fields showed some peculiarities. Before the filament activation, we observed a temporal increase of the converging flows towards the filament's spine. In addition, the mean squared velocity increased temporarily before the activation and peaked just before it, followed by a steep decrease. We further see an increase in the average shear of the zonal flow component in the filament's region, followed by a steep decrease. The photospheric line-of-sight magnetic field shows a persistent increase of induction eastward from the filament spine. The decay index of the magnetic field at heights around 10 Mm shows a value larger than critical one at the connecting point of the northern filament end. The value of the decay index increases monotonically there until the filament activation. Then, it decreased sharply.

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Section: Analysed Datasetsmentioning

confidence: 99%

Evolution of photospheric flows under an erupting filament in the quiet-Sun region

Wollmann

Švanda

Korda

et al. 2020

A&A

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“…5), which is the full-disk velocity map with a size of 586×586 pixel 2 . We further removed the (x, y) velocity signal associated with the motions of the SDO satellite and Earth's orbital displacements from the CST velocity maps following the procedure described by Rincon et al (2017).…”

Section: Horizontal Velocitymentioning

confidence: 99%

“…10 in Roudier et al 2013). The processing steps of the Dopplergrams were to remove Doppler shift associated with the proper motion of satellite and Earth displacement from the raw Doppler signal (see Rincon et al 2017). Then in the Doppler data we corrected a polynomial radial limbshift function adjusted from ring averages of two hours of data.…”

Section: Dopplergramsmentioning

confidence: 99%

Horizontal photospheric flows trigger a filament eruption

Roudier

Schmieder

Filippov

et al. 2018

A&A

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Context. A large filament composed principally of two sections erupted sequentially in the southern hemisphere on January 26 2016. The central, thick part of the northern section was first lifted up and lead to the eruption of the full filament. This event was observed in Hα with the Global Oscillation Network Group (GONG) and Christian Latouche IMageur Solaire (CLIMSO), and in ultraviolet (UV) with the Atmospheric Imaging Assembly (AIA) imager on board the Solar Dynamic Observatory (SDO). Aims. The aim of the paper is to relate the photospheric motions below the filament and its environment to the eruption of the filament.Methods. An analysis of the photospheric motions using Solar Dynamic Observatory Helioseismic and Magnetic Imager (SDO/HMI) continuum images with the new version of the coherent structure tracking (CST) algorithm developed to track granules, as well as large-scale photospheric flows, has been performed. Following velocity vectors, corks migrate towards converging areas.Results. The supergranule pattern is clearly visible outside the filament channel but difficult to detect inside because the modulus of the vector velocity is reduced in the filament channel, mainly in the magnetized areas. The horizontal photospheric flows are strong on the west side of the filament channel and oriented towards the filament. The ends of the filament sections are found in areas of concentration of corks. Whirled flows are found locally around the feet. Conclusions. The strong horizontal flows with an opposite direction to the differential rotation create strong shear and convergence along the magnetic polarity inversion line (PIL) in the filament channel. The filament has been destabilized by the converging flows, which initiate an ascent of the middle section of the filament until the filament reaches the critical height of the torus instability inducing, consequently, the eruption. The n decay index indicated an altitude of 60 Mm for the critical height. It is conjectured that the convergence along the PIL is due to the large-scale size cells of convection that transport the magnetic field to their borders.

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“…Comparisons between theory and observations of supergranular-scale flow fields are usually based on the power spectrum of horizontal surface flows (e.g., Rincon et al 2017). However, it is clear that the power spectrum does not contain much information about the spatial pattern of the flow field, apart from the scale-dependence of the amplitude.…”

Section: Introductionmentioning

confidence: 99%

“…In this case, the Fourier components of the solution would not be independent but would show some dependence that might be measurable. Supergranular dynamics are strongly nonlinear according to Rincon et al (2017) and divergence maps have a large nonzero skewness (Duvall & Gizon 2000). This should be reflected in the bispectrum.…”

Section: Introductionmentioning

confidence: 99%

Characterizing the spatial pattern of solar supergranulation using the bispectrum

Böning

Birch

Gizon

et al. 2020

A&A

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Context. The spatial power spectrum of supergranulation does not fully characterize the underlying physics of turbulent convection. For example, it does not describe the non-Gaussianity in the horizontal flow divergence. Aims. Our aim is to statistically characterize the spatial pattern of solar supergranulation beyond the power spectrum. The next-order statistic is the bispectrum. It measures correlations of three Fourier components and is related to the nonlinearities in the underlying physics. It also characterizes how a skewness in the dataset is generated by the coupling of three Fourier components. Methods. We estimated the bispectrum of supergranular horizontal surface divergence maps that were obtained using local correlation tracking (LCT) and time-distance helioseismology (TD) from one year of data from the Helioseismic and Magnetic Imager on-board the Solar Dynamics Observatory starting in May 2010. Results. We find significantly nonzero and consistent estimates for the bispectrum using LCT and TD. The strongest nonlinearity is present when the three coupling wave vectors are at the supergranular scale. These are the same wave vectors that are present in regular hexagons, which have been used in analytical studies of solar convection. At these Fourier components, the bispectrum is positive, consistent with the positive skewness in the data and consistent with supergranules preferentially consisting of outflows surrounded by a network of inflows. We use the bispectral estimates to generate synthetic divergence maps that are very similar to the data. This is done by a model that consists of a Gaussian term and a weaker quadratic nonlinear component. Using this method, we estimate the fraction of the variance in the divergence maps from the nonlinear component to be of the order of 4-6%.Conclusions. We propose that bispectral analysis is useful for understanding the dynamics of solar turbulent convection, for example for comparing observations and numerical models of supergranular flows. This analysis may also be useful to generate synthetic flow fields.

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Supergranulation and multiscale flows in the solar photosphere

Cited by 33 publications

References 47 publications

Evolution of photospheric flows under an erupting filament in the quiet-Sun region

Evolution of photospheric flows under an erupting filament in the quiet-Sun region

Horizontal photospheric flows trigger a filament eruption

Characterizing the spatial pattern of solar supergranulation using the bispectrum

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