Interpretation of<i>HINODE</i>SOT/SP asymmetric Stokes profiles observed in the quiet Sun network and internetwork

Viticchiè, B.; Alméida, J. Sánchez; Moro, D. Del; Berrilli, F.

doi:10.1051/0004-6361/201015391

Cited by 43 publications

(38 citation statements)

References 38 publications

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“…In agreement with the turbulent dynamo scenario, quiet Sun magnetic fields come with strengths in the full range from almost zero to 2 kG (Sánchez Almeida & Lites 2000;Domínguez Cerdeña et al 2006;Martínez González et al 2008;Bommier et al 2009;Viticchié et al 2011). Even if they only fill a small fraction of the quiet photosphere, the part with strong kG fields may be particularly important for a number of reasons.…”

Section: Introductionmentioning

confidence: 72%

Center-to-limb variation of the area covered by magnetic bright points in the quiet Sun

Bonet

Cabello

Alméida

2012

A&A

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Context. The quiet Sun magnetic fields produce ubiquitous bright points (BPs) that cover a significant fraction of the solar surface. Their contribution to the total solar irradiance (TSI) is so-far unknown. Aims. We aim at measuring the center-to-limb variation (CLV) of the fraction of solar surface covered by quiet Sun magnetic bright points. The fraction is referred to as the fraction of covered surface (FCS). Methods. We count the area covered by BPs in G-band images obtained at various heliocentric angles with the 1-m Swedish Solar Telescope on La Palma. We restore the images to bring them close to the diffraction limit of the instrument (∼0. 1).Results. The FCS is largest at the disk center ( 1%), and then drops down to become 0.2% at μ 0.3 (where μ is the cosine of the heliocentric angle). The relationship has a large scatter, which we evaluate by comparing different subfields within our FOVs. We develop a toy-model to describe the observed CLV, which considers the BPs as depressions in the mean solar photosphere characterized by a depth, a width, and a spread in the inclinations. Although the model is poorly constrained by observations, it shows the BPs to be shallow structures (depth < width) with a large range of inclinations. We also estimate how different parts of the solar disk may contribute to the TSI variations, finding that 90% is contributed by BPs with μ > 0.5, and half of it is due to BPs with μ > 0.8.

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Section: Introductionmentioning

confidence: 72%

Center-to-limb variation of the area covered by magnetic bright points in the quiet Sun

Bonet

Cabello

Alméida

2012

A&A

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“…Using a scalar parameter like the area asymmetry to describe the many different spectral features that a Stokes V profile can present can be perceived as simplistic considering the magnetically and thermodynamically complex atmospheres in which it is formed. Studies and classifications of those shapes have been made and interpreted in the past (Sánchez Almeida & Lites 1992; Viticchié et al 2011) and we refer to them for details on this aspect of asymmetries. No doubt, a scalar like the area asymmetry hides all that richness and we should worry about the possibility that our conclusions could be polluted or invalidated because of that reason.…”

Section: Statistics Of Area Asymmetries Of the Stokes V Profilementioning

confidence: 99%

Scales of the magnetic fields in the quiet Sun

Ariste¹,

Dalda

2012

A&A

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Context. The presence of a turbulent magnetic field in the quiet Sun has been unveiled observationally using different techniques. The magnetic field is quasi-isotropic and has field strengths weaker than 100 G. It is pervasive and may host a local dynamo. Aims. We aim to determine the length scale of the turbulent magnetic field in the quiet Sun. Methods. The Stokes V area asymmetry is sensitive to minute variations in the magnetic topology along the line of sight. Using data provided by Hinode-SOT/SP instrument, we performed a statistical study of this quantity. We classified the different magnetic regimes and infer properties of the turbulent magnetic regime. In particular we measured the correlation length associated to these fields for the first time.Results. The histograms of Stokes V area asymmetries reveal three different regimes: one organized, quasi-vertical and strong field (flux tubes or other structures of the like); a strongly asymmetric group of profiles found around field concentrations; and a turbulent isotropic field. For the last, we confirm its isotropy and measure correlation lengths from hundreds of kilometers down to 10 km, at which point we lost sensitivity. A crude attempt to measure the power spectra of these turbulent fields is made. Conclusions. In addition to confirming the existence of a turbulent field in the quiet Sun, we give further prove of its isotropy. We also measure correlation lengths down to 10 km. The combined results show magnetic fields with a large span of length scales, as expected from a turbulent cascade.

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“…High spatial resolution observations reveal that facular regions break into clusters of bright points, small pores, and facular granular cells (Dunn & Zirker 1973;Title et al 1992;Berger et al 2004;Lites et al 2004;Narayan & Scharmer 2010;Kobel et al 2011;Viticchié et al 2011). It is thought that these features appear as a consequence of the presence of small-scale magnetic elements (or flux tubes) of the size of hundreds of kilometers and magnetic field strength of the order of 1−2 kG (Stenflo 1973;Solanki 1993).…”

Section: Introductionmentioning

confidence: 99%

The possible origin of facular brightness in the solar atmosphere

Костик

Khomenko

2016

A&A

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This paper studies the dependence of the Ca ii H line core brightness on the strength and inclination of the photospheric magnetic field, and on the parameters of convective and wave motions in a facular region at the center of the solar disc. We use three simultaneous data sets that were obtained at the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife): (1) spectra of Ba ii 4554 Å line, registered with the instrument TESOS to measure the variations of intensity and velocity through the photosphere up to the temperature minimum; (2) spectropolarimetric data in Fe i 1.56 µm lines (registered with the instrument TIP II) to measure photospheric magnetic fields; (3) filtergrams in Ca ii H that give information about brightness fluctuations in the chromosphere. The results show that the Ca ii H brightness in the facula strongly depends on the power of waves with periods in the 5-min range, which propagate upwards, and also on the phase shift between velocity oscillations at the bottom photosphere and around the temperature minimum height that is measured from Ba ii line. The Ca ii H brightness is maximum at locations where the phase shift between temperature and velocity oscillations lies within 0 • -100 • . There is an indirect influence of convective motions on the Ca ii H brightness. The higher the amplitude of convective velocities is and the greater the height is where they change their direction of motion, the brighter the facula. In summary, our results lead to conclusions that facular regions appear bright not only because of the Wilson depression in magnetic structures, but also owing to real heating.

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Interpretation ofHINODESOT/SP asymmetric Stokes profiles observed in the quiet Sun network and internetwork

Cited by 43 publications

References 38 publications

Center-to-limb variation of the area covered by magnetic bright points in the quiet Sun

Center-to-limb variation of the area covered by magnetic bright points in the quiet Sun

Scales of the magnetic fields in the quiet Sun

The possible origin of facular brightness in the solar atmosphere

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