THE SCATTERING POLARIZATION OF THE Lyα LINES OF H I AND He II TAKING INTO ACCOUNT PARTIAL FREQUENCY REDISTRIBUTION AND
                    <i>J</i>
                    -STATE INTERFERENCE EFFECTS

Belluzzi, L.; Bueno, J. Trujillo; Štěpán, Jiří

doi:10.1088/2041-8205/755/1/l2

Cited by 40 publications

(32 citation statements)

References 14 publications

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“…These conclusions were reached through detailed radiative transfer calculations in semi-empirical and hydrodynamical models of the solar atmosphere, assuming complete frequency redistribution (CRD) and neglecting quantum interference between the two upper levels of the Lyα line (seeŠtěpán & Trujillo Bueno (2011) for details on the atomic model and numerical method of solution). As shown by Belluzzi et al (2012), these last two approximations are suitable for estimating the polarization sig- The above-mentioned investigations were carried out using one-dimensional models of the extended solar atmosphere, such as the semi-empirical models of Fontenla et al (1993) and the hydrodynamical models of Carlsson & Stein (1997). However, both observations (e.g., Vourlidas et al 2010) and simulations (e.g., Leenaarts et al 2012) show that the outer solar atmosphere is highly structured and dynamic, departing radically from a uniform, plane-parallel configuration.…”

Section: Introductionmentioning

confidence: 84%

THE HANLE EFFECT OF Lyα IN A MAGNETOHYDRODYNAMIC MODEL OF THE SOLAR TRANSITION REGION

Štěpán

Bueno

Carlsson

et al. 2012

ApJ

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In order to understand the heating of the solar corona it is crucial to obtain empirical information on the magnetic field in its lower boundary (the transition region). To this end, we need to measure and model the linear polarization produced by scattering processes in strong UV lines, such as the hydrogen Lyα line. The interpretation of the observed Stokes profiles will require taking into account that the outer solar atmosphere is highly structured and dynamic, and that the height of the transition region may well vary from one place in the atmosphere to another. Here we report on the Lyα scattering polarization signals we have calculated in a realistic model of an enhanced network region, resulting from a state-of-the-art radiation MHD simulation. This model is characterized by spatially complex variations of the physical quantities at transition region heights. The results of our investigation lead us to emphasize that scattering processes in the upper solar chromosphere should indeed produce measurable linear polarization in Lyα. More importantly, we show that via the Hanle effect the model's magnetic field produces significant changes in the emergent Q/I and U/I profiles. Therefore, we argue that by measuring the polarization signals produced by scattering processes and the Hanle effect in Lyα and contrasting them with those computed in increasingly realistic atmospheric models, we should be able to decipher the magnetic, thermal and dynamic structure of the upper chromosphere and transition region of the Sun.

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Section: Introductionmentioning

confidence: 84%

THE HANLE EFFECT OF Lyα IN A MAGNETOHYDRODYNAMIC MODEL OF THE SOLAR TRANSITION REGION

Štěpán

Bueno

Carlsson

et al. 2012

ApJ

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“…When the hyperfine structure is neglected, by artificially assuming a zero nuclear spin I = 0 in place of the real nuclear spin I = 3/2, as we do for some calculations presented below, this element matrix number reduces to 40, 4 of which belong to the lower term. The effect of the transition from the Zeeman effect to the Paschen-Back effect on the level energy differences and proper wavevector components is taken into account as described in Bommier (1980). The global spontaneous emission probability…”

Section: The Model Atommentioning

confidence: 99%

“…The code is built about the statistical equilibrium code developed following Bommier (1980). This code does not use the tensorial algebra for developing the atomic density matrix, which is developed over the dyadic basis instead.…”

Section: Code Structurementioning

confidence: 99%

“…The reason is that the code is aimed to be valid under the incomplete Paschen-Back conditions (or the analogous conditions for the hyperfine structure). As already explained in Bommier (1980), in this case the number of possibly non-zero matrix elements developed on the tensorial basis is not reduced with respect to the number of elements when the matrix is projected onto the dyadic basis and the transformation of the equations into the tensorial basis is a supplementary effort leading to more complex equations. The novelty of the present formalism is that the density matrix now depends on the atomic velocity, and that the statistical equilibrium has to be resolved for each atomic velocity class.…”

Section: Code Structurementioning

confidence: 99%

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Master equation theory applied to the redistribution of polarized radiation in the weak radiation field limit

Bommier

2016

A&A

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Context. The spectrum of the linear polarization, which is formed by scattering and observed on the solar disk close to the limb, is very different from the intensity spectrum and thus able to provide new information, in particular about anisotropies in the solar surface plasma and magnetic fields. In addition, a large number of lines show far wing polarization structures assigned to partial redistribution (PRD), which we prefer to denote as Rayleigh/Raman scattering. The two-level or two-term atom approximation without any lower level polarization is insufficient for many lines. Aims. In the previous paper of this series, we presented our theory generalized to the multilevel and multiline atom and comprised of statistical equilibrium equations for the atomic density matrix elements and radiative transfer equation for the polarized radiation.The present paper is devoted to applying this theory to model the second solar spectrum of the Na i D1 and D2 lines.Methods. The solution method is iterative, of the lambda-iteration type. The usual acceleration techniques were considered or even applied, but we found these to be unsuccessful, in particular because of nonlinearity or large number of quantities determining the radiation at each depth. Results. The observed spectrum is qualitatively reproduced in line center, but the convergence is yet to be reached in the far wings and the observed spectrum is not totally reproduced there. Conclusions. We need to investigate noniterative resolution methods. The other limitation lies in the one-dimensional (1D) atmosphere model, which is unable to reproduce the intermittent matter structure formed of small loops or spicules in the chromosphere. This modeling is rough, but the computing time in the presence of hyperfine structure and PRD prevents us from envisaging a threedimensional (3D) model at this instant.

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“…Interestingly, the bright plage region and some of the network features that can be distinguished in the Stokes I image show nearly zero linear polarization in the Stokes Q/I image, while the surrounding quiet regions instead show very significant polarization signals. In a forthcoming publication we will in-vestigate whether this can be explained on the basis of the results reported above, by noting that the broadband Q/I signals observed by CLASP are dominated by the linear polarization in the Lyα wings (see Belluzzi et al 2012) and by bearing in mind that plages and the network have stronger magnetic fields than the surrounding quieter regions.…”

Section: A Look At Observational Data: Claspmentioning

confidence: 96%

Magnetic Sensitivity in the Wing Scattering Polarization Signals of the Hydrogen Lyman-α Line of the Solar Disk Radiation

Ballester

Belluzzi

Bueno

2019

ApJ

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The linear polarization produced by scattering processes in the hydrogen Lyα line of the solar disk radiation is a key observable for probing the chromosphere-corona transition region (TR) and the underlying chromospheric plasma. While the line-center signal encodes information on the magnetic field and the three-dimensional structure of the TR, the sizable scattering polarization signals that the joint action of partial frequency redistribution and J-state interference produce in the Lyα wings have generally been thought to be sensitive only to the thermal structure of the solar atmosphere. Here we show that the wings of the Q/I and U/I scattering polarization profiles of this line are actually sensitive to the presence of chromospheric magnetic fields, with strengths similar to those that produce the Hanle effect in the line core (i.e., between 5 and 100 gauss, approximately). In spite of the fact that the Zeeman splitting induced by such weak fields is very small compared to the total width of the line, the magneto-optical effects that couple the transfer equations for Stokes Q and U are actually able to produce sizable changes in the Q/I and U/I wings. We find that magnetic fields with longitudinal components larger than 100 G produce an almost complete depolarization of the wings of the Lyα Q/I profiles within a ±5 Å spectral range around line center, while stronger fields are required for the U/I wing signals to be depolarized to a similar extent. The theoretical results presented here further expand the diagnostic content of the unprecedented spectropolarimetric observations provided by the Chromospheric Lyman-Alpha Spectropolarimeter (CLASP).

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THE SCATTERING POLARIZATION OF THE Lyα LINES OF H I AND He II TAKING INTO ACCOUNT PARTIAL FREQUENCY REDISTRIBUTION AND J -STATE INTERFERENCE EFFECTS

Cited by 40 publications

References 14 publications

THE HANLE EFFECT OF Lyα IN A MAGNETOHYDRODYNAMIC MODEL OF THE SOLAR TRANSITION REGION

THE HANLE EFFECT OF Lyα IN A MAGNETOHYDRODYNAMIC MODEL OF THE SOLAR TRANSITION REGION

Master equation theory applied to the redistribution of polarized radiation in the weak radiation field limit

Magnetic Sensitivity in the Wing Scattering Polarization Signals of the Hydrogen Lyman-α Line of the Solar Disk Radiation

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