Non-perturbative theory of radiative scattering in the weak radiation field limit: Resolution of Egidio Landi's "paradox" - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2020

Non-perturbative theory of radiative scattering in the weak radiation field limit: Resolution of Egidio Landi's "paradox"

Résumé

This work is aimed to the interpretation of the linear polarization spectrum observed in the “Second Solar Spectrum”, likely to provide information on the magnetic field vector or on the medium anisotropy. The lines are formed by scattering. Far wings due to partial redistribution are observed in 30% of the spectral lines (Belluzzi & Landi Degl’Innocenti, 2009, A&A, 495, 577). It will be first shown that the second-order perturbation theory is unable to fully describe the frequency redistribution in the far wings. Rayleigh/Raman scattering appears at fourth order. The development has then to be pursued beyond. It will be shown how this series development can be transformed into an infinite sum, which can then be evaluated at infinity, thus overcoming the Markov approximation. In a second part, addressing the problem of the scattering by multilevel atoms, the different processes entering the redistribution will be discussed, which are namely the Rayleigh/Raman scattering and the coupling between the frequency coherence and the Doppler effect in the laboratory reference frame. These two processes are different, but it will be shown they are weighted by part of the same collisions in the redistribution description. The consequences of this will be discussed, in terms of redistribution model. It will be shown that the statistical equilibrium equations have to be resolved for each atomic velocity class, leading to departures from the Maxwellian distribution in the excited states.
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Dates et versions

hal-03025281 , version 1 (10-12-2020)

Identifiants

  • HAL Id : hal-03025281 , version 1

Citer

Véronique Bommier. Non-perturbative theory of radiative scattering in the weak radiation field limit: Resolution of Egidio Landi's "paradox". 8th International Workshop on Solar Polarization (SPW8), in honor of Egidio Landi Degl'Innocenti, Sep 2016, Florence, Italy. pp.17-18. ⟨hal-03025281⟩
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