Asymmetries and wavelengths of solar spectral lines and the solar rotation determined from Fourier-transform spectra

Balthasar, H.

doi:10.1007/bf02270836

Cited by 61 publications

(37 citation statements)

References 35 publications

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“…11. This alignment also eliminates the influence of the limb effect on the Fe lines, except for a possible differential limb effect between the Fe I lines and the Fe II line, which is on the order of 150 ms −1 (Balthasar 1984). Using the same analysis as before, we find the Fe II emission line near the limb very close to its nominal position.…”

Section: Doppler Shiftssupporting

confidence: 58%

Dynamics of the Fe II 396.94 nm emission line observed at solar disk center

Schmidt

Fisher

2013

A&A

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Aims. We have studied the structure and dynamics of the upper photosphere and lower chromosphere of the quiet Sun. Methods. We analyzed a sequence of scans of slit spectra of the Ca II H line at 396.8 nm, with a spectral resolution of 850 000, and a spatial resolution of about one arcsec, taken in the quiet Sun at disk center, with a duration of about 55 min and an area coverage of 185 × 3.5 . We used statistical methods to characterize size, lifetime, and dynamics of emission features of the Fe II line at 396.94 nm. Results. We have identified about 780 distinct features where the Fe II line shows emission stronger than 3% above the local continuum. Their lifetime is on the order of one minute, and the spatial extent is about or less than 2 . On average, Fe II emission features show a significant redshift of 1.3 km s −1 , with respect to the position of the absorption line. The redshift of the Fe II emission is absent close to the solar limb. The Fe II emission is coupled with a strongly enhanced intensity level of the Ca II wings. A time line analysis shows that other photospheric lines show significant redshift one minute before, and a blueshift after, the occurrence of an emission event. A redshift of the Ca II H line core precedes the redshift of the Fe II line by about 30 s. The occurrence of the H2v emissions is strongly reduced before and significantly increased after the Fe II emission events. Conclusions. The temporal behavior of the Fe II emission line and both the Ca II H line core and H2v emission suggest a connection between Fe II emission and chromospheric activity. The presence of a significant redshift during the Fe II emissions and the absence of this redshift near the limb suggest that the observed redshift is indeed caused by a downflow in the line-forming region. From our result concerning the intensity fluctuations in the core of the Fe II line, and from the magnitude of the downflow velocities we conclude that the Fe II emissions at 396.94 nm occur in the photosphere.

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Section: Doppler Shiftssupporting

confidence: 58%

Dynamics of the Fe II 396.94 nm emission line observed at solar disk center

Schmidt

Fisher

2013

A&A

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“…The convective blueshift is a shift of spectral lines of up to 500 m s -1 caused by solar granulation (Beckers and Nelson, 1978). The blueshift is strongest at the disk center and shows a center-to-limb variation, which is also known as the "limb effect" (see, e.g.…”

Section: Convective Blueshift and Limb Effectmentioning

confidence: 99%

“…The blueshift is strongest at the disk center and shows a center-to-limb variation, which is also known as the "limb effect" (see, e.g. Balthasar, 1984). The limb effect further complicates Doppler measurements on the solar surface, as it cannot be averaged out by taking longer time series.…”

Section: Convective Blueshift and Limb Effectmentioning

confidence: 99%

A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

Doerr¹,

Steinmetz²,

Holzwarth³

et al. 2012

Sol Phys

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“…The LOS velocity was calculated by fitting a Gaussian profile to the four wavelength points sampling the Fe i line (±40 and ±80 mÅ relative to 5250.217 Å) and correcting for the convection, solar rotation (see Balthasar 1984), and shifts caused by the instrumental configuration. The CLV of wavelength shift introduced by the granulation was compensated for by using the results of Balthasar et al (1985).…”

Section: Line-of-sight Velocitymentioning

confidence: 99%

Centre-to-limb properties of small, photospheric quiet-Sun jets

Costa

Solanki

Danilović

et al. 2015

A&A

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Context. Strongly Doppler-shifted Stokes V profiles have been detected in the quiet Sun with the IMaX instrument on-board the SUNRISE stratospheric balloon-borne telescope. High velocities are required to produce such signals, hence these events have been interpreted as jets, although other sources are also possible. Aims. We aim to characterize the variation of the main properties of these events (occurrence rate, lifetime, size, and velocities) with their position on the solar disk between disk centre and the solar limb. Methods. These events were identified in SUNRISE/IMaX data according to the same objective criteria at all available positions on the solar disk. Their properties were determined using standard techniques. Results. Our study yielded a number of new insights into this phenomenon. Most importantly, the number density of these events is independent of the heliocentric angle, meaning that the investigated supersonic flows are nearly isotropically distributed. Size and lifetime are also nearly independent of the heliocentric angle, while their intensity contrast increases towards the solar limb. The Stokes V jets are associated with upflow velocities deduced from Stokes I, which are stronger towards the limb. Their intensity decreases with time, while their line-of-sight velocity does not display a clear temporal evolution. Their association with linear polarization signals decreases towards the limb. Conclusions. The density of events appears to be independent of heliocentric angle, establishing that they are directed nearly randomly. If these events are jets triggered by magnetic reconnection between emerging magnetic flux and the ambient field, then our results suggest that there is no preferred geometry for the reconnection process.

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Asymmetries and wavelengths of solar spectral lines and the solar rotation determined from Fourier-transform spectra

Cited by 61 publications

References 35 publications

Dynamics of the Fe II 396.94 nm emission line observed at solar disk center

Dynamics of the Fe II 396.94 nm emission line observed at solar disk center

A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

Centre-to-limb properties of small, photospheric quiet-Sun jets

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