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Hathaway, David H.; Beck, J. G.; Bogart, R. S.; Bächmann, K.; Khatri, G.; Petitto, J. M.; Han, S.; Raymond, J. C.

doi:10.1023/a:1005200809766

Cited by 127 publications

(139 citation statements)

References 19 publications

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“…This spectrum displays three features: (i) the supergranulation peak, (ii) a minimum in the kinetic energy density at 10 Mm and (iii) a slow monotonic increase towards the small scales. Feature (ii) was also found by Hathaway et al (2000) in the Doppler measurements from SOHO/MDI; their spherical harmonic spectrum shows a minimum near = 400 which corresponds to λ = 11 Mm, quite close to our value.…”

Section: Horizontal Velocity Fieldssupporting

confidence: 90%

“…This result confirms the one of Hathaway et al (2000), who used only one velocity component (the radial velocity) of the flow field. As far as the vertical velocity is concerned, the granulation scale clearly emerges at 1.7 Mm.…”

Section: Large Scalessupporting

confidence: 89%

“…However, kinetic energy spectra derived from the radial velocity measured by SOHO/MDI (i.e. from dopplergrams) do show a rise of the spectral kinetic energy density at a scale of 11 Mm and a peak at 36 Mm (Hathaway et al 2000). These results are clearly confirmed by the recent measurement of the horizontal surface flows at disc centre with the wide-field high resolution camera CALAS at Pic-du-Midi ).…”

Section: Introductionsupporting

confidence: 72%

“…To verify this point, we analysed other data from various sources (other Hinode fields, some data from the TRACE satellite). The results, together with those obtained from SOHO/MDI data by Hathaway et al (2000) 2 are summarised in Table 1. These data indeed show some variability both in the location of the peak and its amplitude.…”

Section: Horizontal Velocity Fieldsmentioning

confidence: 96%

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On the power spectrum of solar surface flows

Rieutord

Roudier

Rincon

et al. 2010

A&A

113

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Context. The surface of the Sun provides us with a unique and very detailed view of turbulent stellar convection. Studying its dynamics can therefore help us make significant progress in stellar convection modelling. Many features of solar surface turbulence like the supergranulation are still poorly understood. Aims. The aim of this work is to give new observational constraints on these flows by determining the horizontal scale dependence of the velocity and intensity fields, as represented by their power spectra, and to offer some theoretical guidelines to interpret these spectra. Methods. We use long time-series of images taken by the Solar Optical Telescope (SOT) on board the Hinode satellite; we reconstruct both horizontal (by granule tracking) and vertical (by Doppler effect) velocity fields in a field-of-view of ∼ 75×75 Mm 2 . The dynamics in the subgranulation range can be investigated with unprecedented precision thanks to the absence of seeing effects and the use of the modulation transfer function of SOT for correcting the spectra. Results. At small subgranulation scales down to 0.4 Mm the spectral density of kinetic energy associated with vertical motions exhibits a k −10/3 -like power law, while the intensity fluctuation spectrum follows either a k −17/3 or a k −3 -like power law at the two continuum levels investigated (525 and 450 nm respectively). We discuss the possible physical origin of these scalings and interpret the combined presence of k −17/3 and k −10/3 power laws for the intensity and vertical velocity as a signature of buoyancy-driven turbulent dynamics in a strongly thermally diffusive regime. In the mesogranulation range and up to a scale of 25 Mm, we find that the amplitude of the vertical velocity field decreases like λ −3/2 with the horizontal scale λ. This behaviour corresponds to a k 2 spectral power law. Still in the 2.5-10 Mm mesoscale range, we find that intensity fluctuations in the blue continuum also follow a k 2 power law. In passing we show that granule tracking cannot sample scales below 2.5 Mm. We finally further confirm the presence of a significant supergranulation energy peak at 30 Mm in the horizontal velocity power spectrum and show that the emergence of a pore erases this spectral peak. We tentatively estimate the scale height of the vertical velocity field in the supergranulation range and find 1 Mm; this value suggests that supergranulation flows are shallow.

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Section: Horizontal Velocity Fieldssupporting

confidence: 90%

Section: Large Scalessupporting

confidence: 89%

Section: Introductionsupporting

confidence: 72%

Section: Horizontal Velocity Fieldsmentioning

confidence: 96%

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On the power spectrum of solar surface flows

Rieutord

Roudier

Rincon

et al. 2010

A&A

113

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“…In particular, even a simple visual inspection of Doppler images of the quiet Sun clearly reveals the pattern of supergranulation flow "cells", whose trademark signature is a peak around ∼ 120 − 130 (35 Megameters, Mm) in the spherical-harmonics energy spectrum of Doppler-projected velocities (Hathaway et al 2000;Williams et al 2014;Hathaway et al 2015). The physical origin of this supergranulation is widely debated (Rieutord & Rincon 2010).…”

Section: Introductionmentioning

confidence: 99%

Supergranulation and multiscale flows in the solar photosphere

Rincon

Roudier

Schekochihin

et al. 2017

A&A

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The Sun provides us with the only spatially well-resolved astrophysical example of turbulent thermal convection. While various aspects of solar photospheric turbulence, such as granulation (one-Megameter horizontal scale), are well understood, the questions of the physical origin and dynamical organization of larger-scale flows, such as the 30-Megameters supergranulation and flows deep in the solar convection zone, remain largely open in spite of their importance for solar dynamics and magnetism. Here, we present a new critical global observational characterization of multiscale photospheric flows and subsequently formulate an anisotropic extension of the Bolgiano-Obukhov theory of hydrodynamic stratified turbulence that may explain several of their distinctive dynamical properties. Our combined analysis suggests that photospheric flows in the horizontal range of scales between supergranulation and granulation have a typical vertical correlation scale of 2.5 to 4 Megameters and operate in a strongly anisotropic, self-similar, nonlinear, buoyant dynamical regime. While the theory remains speculative at this stage, it lends itself to quantitative comparisons with future highresolution acoustic tomography of subsurface layers and advanced numerical models. Such a validation exercise may also lead to new insights into the asymptotic dynamical regimes in which other, unresolved turbulent anisotropic astrophysical fluid systems supporting waves or instabilities operate.

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The Sun and Space Weather

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Cited by 127 publications

References 19 publications

On the power spectrum of solar surface flows

On the power spectrum of solar surface flows

Supergranulation and multiscale flows in the solar photosphere

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