The line response function of stellar atmospheres and the effective depth of line formation

Beckers, J. M.; Milkey, R. W.

doi:10.1007/bf00152353

Cited by 64 publications

(37 citation statements)

References 3 publications

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“…In order to predict the sensitivity of each of the Doppler velocity instruments to perturbations at different heights in the solar atmosphere, we computed the so-called response functions ( hereafter RFs; see Mein 1971;Beckers & Milkey 1975) of the appropriate Fraunhofer lines, and then convolved them with the wavelength filter responses of the instruments. The calculations took into account changes to the line-of-sight velocity at different times of year.…”

Section: Response Functionsmentioning

confidence: 99%

On the Variation of the Peak Asymmetry of Low‐ℓ SolarpModes

Jiménez-Reyes

Chaplin

Elsworth

et al. 2007

ApJ

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The resonant peaks of solar p modes show small amounts of asymmetry in frequency. Here, we use five independent sets of contemporaneous data, collected over a '8 yr period, to investigate whether peak asymmetry in low angular degree p modes changes over the solar activity cycle. Three of the data sets are from instruments on board the ESA /NASA SOHO spacecraft (GOLF, MDI, and VIRGO/SPM ); and two are from ground-based networks (BiSON and GONG). Evidence for variation in asymmetry, well correlated with the activity cycle, is uncovered in the GOLF and BiSON Doppler velocity data. Suggestions of a similar trend are present in the GONG Doppler velocity data. Apparent changes in the MDI Doppler velocity data are somewhat less significant. Meanwhile, analysis of the SPM intensity data failed to uncover any evidence for significant change of the asymmetry parameter.

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Section: Response Functionsmentioning

confidence: 99%

On the Variation of the Peak Asymmetry of Low‐ℓ SolarpModes

Jiménez-Reyes

Chaplin

Elsworth

et al. 2007

ApJ

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“…2, we introduce small magnetic field fluctuations, linear versus altitude, and directly determine the altitudes where the fluctuations correspond to the synthetic Zeeman shifts. This is equivalent to the weighting-function or response-function method (Mein 1971;Beckers et al 1975) used for the sodium lines by Eibe et al (2001Eibe et al ( , 2002. The results are plotted in Figs.…”

Section: Nlte Line Profilesmentioning

confidence: 99%

Magnetic flux tubes observed with THEMIS/MSDP

Mein¹,

Mein²,

Faurobert³

et al. 2006

A&A

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Aims. We use spectro-polarimetric THEMIS/MSDP data to investigate the 3D structure of solar magnetic-flux tubes across the upper photosphere. Methods. Profiles of the sodium D 1 line 589.6 nm are analysed by the bisector method at different wavelengths from the core to the wings, for several bright features. They are compared to synthetic profiles derived from 2D magnetic models of flux tubes and from the MULTI code for NLTE line profiles. Three different magnetic models of flux tubes are investigated. Model (I) consists of a single flux tube that compensates for the horizontal Lorentz forces exactly, while model (II) uses a compromise between horizontal and vertical components. Model (III), a conglomerate of thinner flux tubes, leads to the best agreement with observations. Results.(1) The combination of seeing effects (small filling factor) with slopes of line profiles, which are different in the flux tubes and the neighbouring quiet sun, account for the decrease in observed magnetic field from line core to line wings in central parts of magnetic features, as well as the decrease in magnetic fluxes integrated over the whole magnetic features. (2) The expansion with height of single magnetic flux tubes (models I and II) accounts for the increase in the size of magnetic features from line wings to line core. (3) Pure thermodynamical criteria characterising Dopplershifts and line-intensity fluctuations of magnetic and non-magnetic features have been proven by observations. Conclusions. We could account for differential Zeeman effects along the D 1 line profile by combining expansion of flux tubes with height, low gas pressure inside flux tubes, and small filling factor due to seeing effects. Better agreement with observations, in particular with respect to magnetic field amplitudes, will probably need 3D models that take velocity fields and horizontal gradients of temperature into account.

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“…Response Functions (hereafter, RF s) describe the effect that perturbations of a given physical parameter have in the emergent line intensity (Mein 1971;Beckers & Milkey 1975;Canfield 1976;Caccin et al 1977). In the past years they have become extensively used for the inversion of line profiles and Stokes spectra (Ruiz Cobo & del Toro Iniesta 1992;Bellot Rubio et al 1997).…”

Section: Calculation Of Response Functionsmentioning

confidence: 99%

Investigation of temperature and velocity fluctuations through the solar photosphere with the Na I D lines

Eibe¹,

Mein²,

Roudier³

et al. 2001

A&A

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Abstract. In this work we explore the diagnostic properties of the Na I D resonance lines by calculating the response functions of their line profiles to temperature and velocity perturbations in the atmosphere. We propose a method to transform spectral line intensity fluctuations measured at several wavelengths into temperature and velocity disturbances at different height levels. Results from tests done with several theoretical models of perturbations are discussed. Perturbations that vary as linear functions of depth are efficiently reproduced. The method also provides good estimations for exponential models. As an example we present an application to solar granulation data obtained with Multichannel Subtractive Double Pass (MSDP) spectroscopy.

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The line response function of stellar atmospheres and the effective depth of line formation

Abstract: The response function defines the response of line profiles to a depth variation of such atmospheric parameters as velocity, magnetic field and turbulence. The properties of this function are derived and compared with the so-called contribution function.

Cited by 64 publications

References 3 publications

On the Variation of the Peak Asymmetry of Low‐ℓ SolarpModes

On the Variation of the Peak Asymmetry of Low‐ℓ SolarpModes

Magnetic flux tubes observed with THEMIS/MSDP

Investigation of temperature and velocity fluctuations through the solar photosphere with the Na I D lines

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