M. Koubiti - Academia.edu (original) (raw)
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Papers by M. Koubiti
Journal of Quantitative Spectroscopy and Radiative Transfer, 1995
ABSTRACT The main ideas of the Frequency Fluctuation Model (FFM), devloped to calculate line shap... more ABSTRACT The main ideas of the Frequency Fluctuation Model (FFM), devloped to calculate line shapes emitted by multi electron ions in hot and dense plasmas, are summarized. The line shape code which has been based on the FFM is particularly useful in accounting for the so-called ion dynamics effect and permits the tracing of the relevant inhomogeneous characteristics of the radiative patterns at each stage of the calculations. Information about the inhomogeneities of a given line is collected through a numerical coarse-graining process giving rise to microfield dressed two-level systems. These systems mimic the main features of the radiative properties of the emitter and are used as a basis to model the radiative redistribution function, a second order plasma radiative property. The second order theory is discussed and a few examples, calculated for complex emitter systems, are shown.
The fluctuations and oscillations observed in turbulent plasmas may affect the line shapes emitte... more The fluctuations and oscillations observed in turbulent plasmas may affect the line shapes emitted by atoms and ions. We investigate several plasma conditions for which a spectroscopic signature of plasma turbulence can be observed. Starting from the simple model of microturbulence for Doppler profile, we examine how information on turbulent fluctuations is obtained in astrophysics and magnetic fusion
plasmas. We recall the potential of a formalism which expresses the measured line shape in function of the probability density function of the fluctuating plasma parameters. New calculations of hydrogen dipole
autocorrelation functions and line shapes are presented for plasmas affected by strong Langmuir turbulence and nonlinear wave collapse. We propose a model using a sequence of envelope solitons for the electric field created by the wave packets and felt by the emitters, and show that the line shape may be dominated by the effect of strong Langmuir turbulence.
New Astronomy Reviews, 2009
An overview of several spectral line shapes studies of common interest in astrophysical and labor... more An overview of several spectral line shapes studies of common interest in astrophysical and laboratory plasmas is presented. For lines dominated by Stark broadening, approaches taking into account the dynamics of numerous perturbers are sometimes required. We briefly recall ab initio simulation techniques and model microfield methods used for such conditions. Together with the impact approximation, such models may also be used for studying the effects on a line profile of a magnetic field of the order of the tesla, allowing the diagnostic of stellar objects or magnetic fusion devices. The problem of the apparent spectral line emitted in a plasma affected by strong fluctuations of the plasma parameters is discussed for the case of optically thin plasmas.
Journal of Quantitative Spectroscopy and Radiative Transfer, 1995
ABSTRACT The main ideas of the Frequency Fluctuation Model (FFM), devloped to calculate line shap... more ABSTRACT The main ideas of the Frequency Fluctuation Model (FFM), devloped to calculate line shapes emitted by multi electron ions in hot and dense plasmas, are summarized. The line shape code which has been based on the FFM is particularly useful in accounting for the so-called ion dynamics effect and permits the tracing of the relevant inhomogeneous characteristics of the radiative patterns at each stage of the calculations. Information about the inhomogeneities of a given line is collected through a numerical coarse-graining process giving rise to microfield dressed two-level systems. These systems mimic the main features of the radiative properties of the emitter and are used as a basis to model the radiative redistribution function, a second order plasma radiative property. The second order theory is discussed and a few examples, calculated for complex emitter systems, are shown.
The fluctuations and oscillations observed in turbulent plasmas may affect the line shapes emitte... more The fluctuations and oscillations observed in turbulent plasmas may affect the line shapes emitted by atoms and ions. We investigate several plasma conditions for which a spectroscopic signature of plasma turbulence can be observed. Starting from the simple model of microturbulence for Doppler profile, we examine how information on turbulent fluctuations is obtained in astrophysics and magnetic fusion
plasmas. We recall the potential of a formalism which expresses the measured line shape in function of the probability density function of the fluctuating plasma parameters. New calculations of hydrogen dipole
autocorrelation functions and line shapes are presented for plasmas affected by strong Langmuir turbulence and nonlinear wave collapse. We propose a model using a sequence of envelope solitons for the electric field created by the wave packets and felt by the emitters, and show that the line shape may be dominated by the effect of strong Langmuir turbulence.
New Astronomy Reviews, 2009
An overview of several spectral line shapes studies of common interest in astrophysical and labor... more An overview of several spectral line shapes studies of common interest in astrophysical and laboratory plasmas is presented. For lines dominated by Stark broadening, approaches taking into account the dynamics of numerous perturbers are sometimes required. We briefly recall ab initio simulation techniques and model microfield methods used for such conditions. Together with the impact approximation, such models may also be used for studying the effects on a line profile of a magnetic field of the order of the tesla, allowing the diagnostic of stellar objects or magnetic fusion devices. The problem of the apparent spectral line emitted in a plasma affected by strong fluctuations of the plasma parameters is discussed for the case of optically thin plasmas.