<i>Spectral Line Formation</i>

Jefferies, J. T.; Blackwell, Donald E.

doi:10.1063/1.3021938

Cited by 31 publications

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“…For the coherent term, a very popular approximation, first introduced by Jefferies and White (1960) and revised by Kueer (1975), is to assume that there is complete frequency redistribution in the line core and purely coherent scattering in the line wings. This approximation, called here the CS approximation, may be written as…”

Section: R162 (16)mentioning

confidence: 99%

Partial frequency redistribution of polarized radiation

Frisch

1996

Sol Phys

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Resonance polarization, which is created by the scattering of an anisotropic radiation field in regions of zero or weak magnetic fields, is strongly dependent on the frequency redistribution taking place during the scatterings. Here we discuss the frequency redistribution matrix relevant to resonance lines, concentrating on linear polarization. First we analyze in detail the redistribution matrix in a zero magnetic field given by the theory of Omont, Smith and Cooper (1972), revisited by Domke and Hubeny (1988). We explain that the linear polarization maxima which may appear in the wings of the Stokes Q profiles of strong resonances lines such as the Ca I 4227 ~ line are coherent frequency redistribution effects. Various approximate forms of the frequency redistribution matrix are also examined. For resonance polarization in a weak magnetic field, we suggest a new expression for the redistribution matrix which can be used at all line frequencies, and is consistent with the condition that the Hanle effect acts only in the line core.

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Section: R162 (16)mentioning

confidence: 99%

Partial frequency redistribution of polarized radiation

Frisch

1996

Sol Phys

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“…In transport calculations it is necessary to separate scattering from absorption because of angular correlation. The problem of line shapes in radiation transport has been described by Jefferies (1968). In the limit of zero density and extremely low temperatures, where all broadening effects other than natural can be neglected, resonance fluorescence represents a single coherent quantum process, i.e., the resonance line is caused by scattering.…”

Section: Resonance Scatteringmentioning

confidence: 99%

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Huebner

Barfield

2014

Astrophysics and Space Science Library

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“…The model we employ to predict the absolute vibrational population densities in the NO, N 2 and O 2 ground and excited electronic states is based on the concept of statistical equilibrium [13], in which the balance between electron impact excitation/deexcitation, population and depopulation by radiative transitions, heavy particle deactivation (quenching and/or chemical reaction) and pre-dissociation, determines the excited state number densities. This model has been used successfully to characterise the excitation of N 2 under auroral conditions [14,15,16,17] and in the dayglow [17], to study O 2 under night-time auroral conditions [18,19] and to study the behaviour of NO under auroral conditions [6,9].…”

Section: Statistical Equilibrium Simulationsmentioning

confidence: 99%

Understanding the Role of Electron-driven Processes in Atmospheric Behaviour

Brunger¹

2004

AIP Conference Proceedings

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Electron-impact excitation plays a major role in emission from aurora and a less significant but nonetheless crucial role in the dayglow and nightglow. For some molecules, such as N 2 , O 2 and NO, electron-impact excitation can be followed by radiative cascade through many different sets of energy levels, producing emission with a large number of lines. We review the application of our statistical equilibrium program to predict this rich spectrum of radiation, and we compare results we have obtained against available independent measurements. In addition, we also review the calculation of energy transfer rates from electrons to N 2 , O 2 and NO in the thermosphere. Energy transfer from electrons to neutral gases and ions is one of the dominant electron cooling processes in the ionosphere, and the role of vibrationally excited N 2 and O 2 in this is particularly significant. The importance of the energy dependence and magnitude of the electron-impact vibrational cross sections in the calculation of these rates is assessed.

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Spectral Line Formation

Cited by 31 publications

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Partial frequency redistribution of polarized radiation

Partial frequency redistribution of polarized radiation

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Understanding the Role of Electron-driven Processes in Atmospheric Behaviour

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