Rapid Variations in Intergranular Space

Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig, W.; Staiger, J.

doi:10.1017/s0252921100029122

Cited by 31 publications

(56 citation statements)

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“…This agrees well with the findings obtained from high-resolution spectra that in active regions the granular velocity shifts almost disappear, but that the lines are somewhat broadened (e.g. Nesis et al 1993). Also, we find that the continuum brightness and contrast are in reasonable agreement with the observations only if lines formed deep in the atmosphere, such as the C i lines, are included.…”

Section: Discussionsupporting

confidence: 92%

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Empirical models of solar magnetic flux-tubes and their non-magnetic surroundings

Frutiger

Solanki

2001

A&A

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Abstract.A powerful method for the analysis of the structure of small scale magnetic elements in the solar photosphere is the inversion of Stokes spectra. In previous papers based on such inversions Bellot Rubio et al. (1997Rubio et al. ( , 1999 and Frutiger et al. (1999) have argued in favor of models with rather different dynamic properties. In this paper we return to this debate and compare results returned by inversions based on new multi-component models applied to several Fe i, Fe ii and C i spectral line profiles obtained in active region plage with a Fourier Transform Spectrometer. These inversions differ from earlier ones by the fact that mass conservation is strictly imposed both inside the magnetic elements and on the surrounding external flow field. These flux-tube models are not only able to reproduce the characteristic Stokes V asymmetries and line-shifts observed in active regions plages or network elements, but also the Stokes I line profiles, including line bisectors. It is confirmed that from the quality of the fits alone it is not possible to distinguish between the steady flow proposed by Bellot Rubio et al. (1997) and the oscillatory model of Frutiger & Solanki (1998). If, however, physical constraints are imposed (e.g. mass conservation or that the flow retains the same direction over height in the flux tube) then the oscillatory model is found to be superior. In addition, the current investigation also provides the first inversion-based model of abnormal granulation.

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Section: Discussionsupporting

confidence: 92%

“…Also, the turbulent velocities are larger in the active region granules (cf. Nesis et al 1993). This correspondence between the properties of the convective cells returned by the inversion and those of abnormal granulation is close (e.g.…”

Section: For Details)mentioning

confidence: 99%

Empirical models of solar magnetic flux-tubes and their non-magnetic surroundings

Frutiger

Solanki

2001

A&A

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“…They showed that, at disk center, both, horizontal gradients in the vertical and horizontal velocity at the full resolution are able to reproduce the broadened line profiles after smearing. They concluded that the broadened profiles observed in the dark lanes by Nesis et al (1992) were not necessarily an indication of supersonic flows, whereas the observations in Nesis et al (1993) of line broadened profiles at the edges of granules, between the granule and the intergranular lane, were more likely due to turbulence caused by supersonic flows. Keller (2006) suggested a simple mechanism able to produce broadened line profiles at the edge of granules with no additional turbulence needed.…”

Section: Line Asymmetries and Shiftsmentioning

confidence: 99%

“…Therefore Nesis et al (1993) proposed to use line broadening as an indirect indicator of such flows. However, Solanki et al (1996) compared the velocity field in 2D granulation simulations with synthesized line profiles and showed that, at disk center, other properties of the downflow lanes can cause comparable line broadening, and pointed out that unresolved vertical velocity gradients can also produce apparent line broadening.…”

Section: Introductionmentioning

confidence: 99%

“…However, Solanki et al (1996) compared the velocity field in 2D granulation simulations with synthesized line profiles and showed that, at disk center, other properties of the downflow lanes can cause comparable line broadening, and pointed out that unresolved vertical velocity gradients can also produce apparent line broadening. They concluded that all line widths observed by Nesis et al (1993) can be attributed to limited resolution.…”

Section: Introductionmentioning

confidence: 99%

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Fast horizontal flows in a quiet sun MHD simulation and their spectroscopic signatures

Vitas

Fischer

Vögler

et al. 2011

A&A

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Numerical simulations of solar surface convection have predicted the existence of supersonic horizontal flows in the photospheric granulation. Recently, the detection of such flows in data from the Hinode satellite was reported. We study supersonic granular flows in detail to understand their signatures in spectral lines and to test the observational detection method used to identify these flows in the Hinode observations. We perform time-dependent 3D radiative MHD numerical simulations and synthesize the Fe i 6302 Å spectral lines at the resolution of the Hinode data for different viewing angles covering the center-limb variation. There is very large variation in the detailed shape of the emergent line profiles depending on the viewing angle and the particular flow properties and orientation. At the full simulation resolution the supersonic flows can even produce distinct satellite lines. After smearing to the Hinode resolution sufficient signature of supersonic motion remains. Our analysis shows that the detection method used to analyze the Hinode data is indeed applicable. However, the detection is very sensitive to ad hoc parameter choices and can also misidentify supersonic flows.

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Granulation and waves

Hirzberger¹

2003

Astron Nachr

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Rapid Variations in Intergranular Space

Abstract: Spectrograms of high spatial resolution taken every 15s reveal rapid variations of the continuum intensity and line width. Variations of the latter seem to be related to Doppler velocity gradients.

Cited by 31 publications

References 1 publication

Empirical models of solar magnetic flux-tubes and their non-magnetic surroundings

Empirical models of solar magnetic flux-tubes and their non-magnetic surroundings

Fast horizontal flows in a quiet sun MHD simulation and their spectroscopic signatures

Granulation and waves

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