2-D multiline spectroscopy of the solar photosphere

Berrilli, F.; Consolini, Giuseppe; Pietropaolo, E.; Caccin, B.; Penza, V.; Lepreti, F.

doi:10.1051/0004-6361:20011421

Cited by 44 publications

(54 citation statements)

References 29 publications

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“…By studying the velocity response functions as in Caccin et al (1977) and Berrilli et al (2002), we found that the major contribution to the measured velocities in Fe I 709.04 nm line originates in a layer 100 km above the photospheric surface.…”

Section: Los Velocity Mapsmentioning

confidence: 95%

The photospheric structure of a solar pore with light bridge

Giordano¹,

Berrilli²,

Moro³

et al. 2008

A&A

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Context. Pores are among the photospheric features that form when the magnetic field emerges onto the solar surface. In pores or sunspots, light bridges are bright features that separate umbral areas into two or more irregular regions. Aims. We study the structure of a solar pore (AR10812) with a light bridge. Methods. We analyzed both broad-band and narrow-band images acquired with the Interferometric BI-dimensional Spectrometer at the adaptive optics channel of the NSO/Dunn Solar Telescope. Narrow-band images acquired in the photospheric Fe I 709.04 nm line were used to determine the line-of-sight velocity field. Results. The roundish shape of the pore allows us to derive the radial profiles of both intensity and vertical velocity. The pore has a downward velocity, of about -200 m s −1 , and is surrounded by an annular downflow structure with an average velocity of about -300 m s −1 with respect to the nearby quiet sun. The light bridge shows a long narrow dark structure running along its axis. Corresponding to this dark lane, we measure a weak upflow of about 70 m s −1 , flanked by a downflow of about 150 m s −1 with respect to the pore. The topology of this velocity structure resembles a convective roll. The anticorrelation between continuum intensity and photospheric velocity may be due to the higher gas pressure in a photospheric field-free cusp, above the light bridge, located between two magnetic walls. We present an analytical model capable of reproducing the observations.

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Section: Los Velocity Mapsmentioning

confidence: 95%

The photospheric structure of a solar pore with light bridge

Giordano¹,

Berrilli²,

Moro³

et al. 2008

A&A

Self Cite

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“…We extracted velocities at two different altitudes. A line chord of 16 pm was used to sample a layer around an altitude of 80 km (Altrock et al 1975;Berrilli et al 2002) and a second chord of 8 pm, deeper in the line, was used to sample the atmosphere around 190 km. In order to detect potential spurious effects associated with the artificial flat-fielding operation, an additional set of spectra was computed from images not flat-fielded (Fig.…”

Section: Vertical Velocity Fieldsmentioning

confidence: 99%

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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“…As is well known, granulation with a typical 1-Mm size and 5-min lifetime are ubiquitous in high-resolution photospheric images (e.g., Title et al 1989;Berrilli et al 2002;Jin et al 2009). Groups of theses granules tend to move in a systematic way, which is characterized by a cellular convective motion at scales of the order of 32 Mm (Leighton et al 1962).…”

Section: Introductionmentioning

confidence: 97%

Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

Potts

Marsch

Attié

et al. 2010

A&A

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Aims. We study horizontal supergranule-scale motions revealed by TRACE observation of the chromospheric emission, and investigate the coupling between the chromosphere and the underlying photosphere. Methods. A highly efficient feature-tracking technique called balltracking has been applied for the first time to the image sequences obtained by TRACE (transition region and coronal explorer) in the passband of white light and the three ultraviolet passbands centered at 1700 Å, 1600 Å, and 1550 Å. The resulting velocity fields have been spatially smoothed and temporally averaged in order to reveal horizontal supergranule-scale motions that may exist at the emission heights of these passbands. Results. We find indeed a high correlation between the horizontal velocities derived in the white-light and ultraviolet passbands. The horizontal velocities derived from the chromospheric and photospheric emission are comparable in magnitude. Conclusions. The horizontal motions derived in the UV passbands might indicate the existence of a supergranule-scale magnetoconvection in the chromosphere, which may shed new light on the study of mass and energy supply to the corona and solar wind at the height of the chromosphere. However, it is also possible that the apparent motions reflect the chromospheric brightness evolution as produced by acoustic shocks which might be modulated by the photospheric granular motions in their excitation process, or advected partly by the supergranule-scale flow towards the network while propagating upward from the photosphere. To reach a firm conclusion, it is necessary to investigate the role of granular motions in the excitation of shocks through numerical modeling, and future high-cadence chromospheric magnetograms must be scrutinized.

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2-D multiline spectroscopy of the solar photosphere

Cited by 44 publications

References 29 publications

The photospheric structure of a solar pore with light bridge

The photospheric structure of a solar pore with light bridge

On the power spectrum of solar surface flows

Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

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