Linear Polarization Measurements of Chromospheric Emission Lines

Sheeley, N. R.; ., Jr.; Keller, Christoph U.

doi:10.1086/376984

Cited by 6 publications

(4 citation statements)

References 26 publications

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“…This plot corresponds to an off-limb observation with the scattering center located at a height of 0.01 R . Whereas the typical trilobate shape of D2 cannot be reproduced by our simple modeling for an optically thin plasma, the shape of D1, and in particular the presence of a central peak in its core, closely resembles observations of this line published in recent work (e.g., Sheeley & Keller 2003). Departures of the line shapes in Figure 3 from typical observations of the D1 and D2 lines are likely to be due to radiative transfer effects and possibly PRD effects.…”

Section: Illustrative Resultssupporting

confidence: 82%

Line Formation Theory for the Multiterm Atom with Hyperfine Structure in a Magnetic Field

Casini

Sainz

2005

ApJ

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Within the framework of the quantum theory of polarized line formation, in the limit of complete frequency redistribution and of the collisionless regime, we derive explicit formulae describing the statistical equilibrium and the radiative emission of a multiterm atom with hyperfine structure, in the presence of an external magnetic field. The formulae we obtained for the radiative rates of the statistical equilibrium equations and for the radiative coefficients of the transfer equation for polarized radiation can be applied to investigate the formation of spectral lines for which both fine-structure and hyperfine-structure effects are important (e.g., the D1 and D2 lines of Na i in the solar atmosphere).

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Section: Illustrative Resultssupporting

confidence: 82%

Line Formation Theory for the Multiterm Atom with Hyperfine Structure in a Magnetic Field

Casini

Sainz

2005

ApJ

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“…On the other hand, the profiles plotted in panel d of Figure 9, obtained assuming a continuum sufficiently strong in order to cancel out all the observational signatures of interferences, are in good qualitative agreement with the off-limb observation presented in figure 5 (top-right panel) of Sheeley & Keller (2003). This illustrates the sensitivity of the theoretical polarization profiles to the parameters of the model.…”

Section: The O I Triplet At 7773 åsupporting

confidence: 82%

“…It should be noticed that the antisymmetric profile which is obtained across transition 1 when interferences between different J-levels and lower-level polarization are taken into account, and when the continuum is not too strong (see the dotted profile in panel c of Figure 9) is very similar to the one observed by Keller & Sheeley (1999) outside the solar limb (see their Figure 5). On the other hand, the profiles plotted in panel d of Figure 9, obtained assuming a continuum sufficiently strong in order to cancel out all the observational signatures of interferences, are in good qualitative agreement with the off-limb observation presented in figure 5 (top-right panel) of Sheeley & Keller (2003). This illustrates the sensitivity of the theoretical polarization profiles to the parameters of the model.…”

Section: If a Continuum ε Csupporting

confidence: 82%

THE IMPACT OF QUANTUM INTERFERENCE BETWEEN DIFFERENTJ-LEVELS ON SCATTERING POLARIZATION IN SPECTRAL LINES

Belluzzi

Bueno

2011

ApJ

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The spectral line polarization produced by optically pumped atoms contains a wealth of information on the thermal and magnetic structure of a variety of astrophysical plasmas, including that of the solar atmosphere. A correct decoding of such information from the observed Stokes profiles requires a clear understanding of the effects that radiatively induced quantum interferences (or coherences) between pairs of magnetic sublevels produce on these observables, in the absence and in the presence of magnetic fields of arbitrary strength. Here we present a detailed theoretical investigation on the role of coherences between pairs of sublevels pertaining to different fine-structure J-levels, clarifying when they can be neglected for facilitating the modeling of the linear polarization produced by scattering processes in spectral lines. To this end, we apply the quantum theory of spectral line polarization and calculate the linear polarization patterns of the radiation scattered at 90 • by a slab of stellar atmospheric plasma, taking into account and neglecting the above-mentioned quantum interferences. Particular attention is given to the 2 S − 2 P, 5 S − 5 P, and 3 P − 3 S multiplets. We point out the observational signatures of this kind of interferences and analyze their sensitivity to the energy separation between the interfering levels, to the amount of emissivity in the background continuum radiation, to lower-level polarization, and to the presence of a magnetic field. Some interesting applications to the following spectral lines are also presented: Ca ii H and K, Mg ii h and k, Na i D 1 and D 2 , the Ba ii 4554 Å and 4934 Å resonance lines, the Cr i triplet at 5207 Å, the O i triplet at 7773 Å, the Mg i b-lines, and the Hα and Lyα lines of H i.

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“…Therefore, we scheduled our final observing run to be only a few weeks after the mirror was realuminized. That final run satisfied my curiosity about the polarizations of chromospheric emission lines and also suggested that chromospheric spicules are the source of the O I scattering polarization (Sheeley & Keller, ). To my knowledge, that result has never been pursued.…”

Section: Forty Years At Nrl In Washington DCmentioning

confidence: 56%

Memorable Events During a Research Career

Sheeley¹

2019

JGR Space Physics

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In this paper, I sketch a path through my research career in solar and heliospheric physics, recalling some memorable events and discoveries that occurred along the way. This chain of events begins with an influential Time magazine article in 1955 and progresses through a summer at Bell Labs, 9 years at Caltech, 7 years at the Kitt Peak National Observatory, 43 years at the Naval Research Laboratory, and ends with a digitized map of the Sun's Ca II K‐Line emission in 1919 when the AGU was born. Accidents and puzzling results are often the keys to progress and should be examined carefully.

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Linear Polarization Measurements of Chromospheric Emission Lines

Cited by 6 publications

References 26 publications

Line Formation Theory for the Multiterm Atom with Hyperfine Structure in a Magnetic Field

Line Formation Theory for the Multiterm Atom with Hyperfine Structure in a Magnetic Field

THE IMPACT OF QUANTUM INTERFERENCE BETWEEN DIFFERENTJ-LEVELS ON SCATTERING POLARIZATION IN SPECTRAL LINES

Memorable Events During a Research Career

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