Resonance Line Transfer with Partial Redistribution. V. The Solar CA II Lines

Shine, R. A.; Milkey, R. W.; Mihalas, Dimitri

doi:10.1086/153744

Cited by 47 publications

(20 citation statements)

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“…Within about 1 Å from line center coherent scattering becomes important (e.g. Shine et al 1975;Ayres 1975;Uitenbroek 1989). LTE is also a good assumption for the line opacity because calcium is predominantly singly ionized throughout the photosphere so that the H and K opacity has small sensitivity to the ultraviolet overionization which complicates the formation of, e.g.…”

Section: Methodsmentioning

confidence: 99%

The wings of Ca II H and K as solar fluxtube diagnostics

Sheminova¹,

Rutten²,

Voort³

2005

A&A

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Abstract. We combine high-resolution Ca  H and K spectrograms from the Swedish Vacuum Solar Telescope with standard fluxtube modeling to derive photospheric temperature and velocity stratifications within individual magnetic elements in plage near a sunspot. We find that 1D on-axis modeling gives better consistency than spatial averaging over flaring-fluxtube geometry. Our best-fit temperature stratifications suggest that magnetic elements are close to radiative equilibrium throughout their photospheres. Their brightness excess throughout the H and K wings compared with the quiet photosphere is primarily due to low density, not to mechanical heating. We conclude that the extended H and K wings provide excellent fine-structure diagnostics for both high-resolution observations and simulations of the solar photosphere.

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Section: Methodsmentioning

confidence: 99%

The wings of Ca II H and K as solar fluxtube diagnostics

Sheminova¹,

Rutten²,

Voort³

2005

A&A

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“…Second, the K 1 and K 2 separations increase towards the limb. First shown by Shine et al (1975) and later confirmed by more accurate modeling by Uitenbroek (1989), the H and K lines must be treated in PRD as modeling assuming CRD cannot reproduce any of the center-to-limb effects. However, it is not possible to accurately model both effects using the same 1D model atmosphere (Shine et al 1975).…”

Section: Center-to-limb Variationmentioning

confidence: 98%

“…The H and K lines are formed much higher, in the less dense upper chromosphere where 3D and PRD effects play an essential role in the line formation (Miyamoto 1953), than the infrared lines. Previously, these lines have been modeled including effects of PRD, but only in a one-dimensional (1D) radiative transfer approach (Vardavas & Cram 1974;Shine et al 1975;Uitenbroek 1989;Solanki et al 1991;Rezaei et al 2008). Using a 3D non-LTE radiative transfer approach including effects of PRD has become feasible recently with an upgrade of the Multi3D code (Sukhorukov & Leenaarts 2017).…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional modeling of the Ca II H and K lines in the solar atmosphere

Bjørgen

Sukhorukov

Leenaarts

et al. 2018

A&A

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Context. CHROMIS, a new imaging spectrometer at the Swedish 1-m Solar Telescope (SST), can observe the chromosphere in the H and K lines of Ca ii at high spatial and spectral resolution. Accurate modeling as well as an understanding of the formation of these lines are needed to interpret the SST/CHROMIS observations. Such modeling is computationally challenging because these lines are influenced by strong departures from local thermodynamic equilibrium, three-dimensional radiative transfer, and partially coherent resonance scattering of photons. Aims. We aim to model the Ca ii H&K lines in 3D model atmospheres to understand their formation and to investigate their diagnostic potential for probing the chromosphere. Methods. We model the synthetic spectrum of Ca ii using the radiative transfer code Multi3D in three different radiationmagnetohydrodynamic model atmospheres computed with the Bifrost code. We classify synthetic intensity profiles according to their shapes and study how their features are related to the physical properties in the model atmospheres. We investigate whether the synthetic data reproduce the observed spatially-averaged line shapes, center-to-limb variation and compare with SST/CHROMIS images.Results. The spatially-averaged synthetic line profiles show too low central emission peaks, and too small separation between the peaks. The trends of the observed center-to-limb variation of the profiles properties are reproduced by the models. The Ca ii H&K line profiles provide a temperature diagnostic of the temperature minimum and the temperature at the formation height of the emission peaks. The Doppler shift of the central depression is an excellent probe of the velocity in the upper chromosphere.

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“…Shine et al 1975). The b l curve first rises from photon losses in the Ca ii infrared lines that are shared through collisional lower-level coupling, then from photon losses in H & K. They offset the Ca ii depletion by ionization that would occur in LTE (dotted curve).…”

Section: Alc7: Eb Diagnostics In 1d Se Modelingmentioning

confidence: 99%

Hαfeatures with hot onsets

Rutten

2016

A&A

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Ellerman bombs are transient brightenings of the wings of the Balmer lines that uniquely mark reconnection in the solar photosphere.They are also bright in strong Ca ii and ultraviolet lines and in ultraviolet continua, but they are not visible in the optical continuum and the Na i D and Mg i b lines. These discordant visibilities invalidate all published Ellerman bomb modeling. I argue that the assumption of Saha-Boltzmann lower-level populations is informative to estimate bomb-onset opacities for these diverse diagnostics, even and especially for Hα, and employ such estimates to gauge the visibilities of Ellerman bomb onsets in all of them. They constrain Ellerman bomb formation to temperatures 10 000−20 000 K and hydrogen densities around 10 15 cm −3 . Similar arguments likely hold for Hα visibility in other transient phenomena with hot and dense onsets.

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Resonance Line Transfer with Partial Redistribution. V. The Solar CA II Lines

Cited by 47 publications

References 0 publications

The wings of Ca II H and K as solar fluxtube diagnostics

The wings of Ca II H and K as solar fluxtube diagnostics

Three-dimensional modeling of the Ca II H and K lines in the solar atmosphere

Hαfeatures with hot onsets

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