Hydrogen Lyman-<i>α</i> and Lyman-<i>β</i> spectral radiance profiles   in the quiet Sun

Curdt, W.; Marsch, E.; Schühle, U.

doi:10.1051/0004-6361/200811445

Cited by 33 publications

(31 citation statements)

References 37 publications

(78 reference statements)

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“…As mentioned in that paper, the emission suffered from geocoronal absorption. After correcting for this effect, their Ly−α profile seems to be flat-topped, which is very different from the strongly reversed Ly−α profiles in the quiet Sun Tian et al 2009). …”

Section: Hydrogen Lyman Line Profilesmentioning

confidence: 82%

“…The average Ly−α profile was found to be strongly reversed and have The O vi intensity has been divided by 600. a stronger blue horn. It is believed that the opposite asymmetries in the average profiles of Ly−α and higher Lyman lines are probably caused by the combined effect of flows in the different layers of the solar atmosphere and opacity differences of the lines (Gunár et al 2008;Tian et al 2009). …”

Section: Hydrogen Lyman Line Profilesmentioning

confidence: 99%

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Solar transition region above sunspots

Curdt

Teriaca

Landi

et al. 2009

A&A

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Aims. We study the transition region (TR) properties above sunspots and the surrounding plage regions, by analyzing several sunspot reference spectra obtained by the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument in March 1999 and November 2006. Methods. We compare the SUMER spectra observed in the umbra, penumbra, plage, and sunspot plume regions. The hydrogen Lyman line profiles averaged in each of the four regions are presented. For the sunspot observed in 2006, the electron densities, differential emission measure (DEM), and filling factors of the TR plasma in the four regions are also investigated.Results. The self-reversals of the hydrogen Lyman line profiles are almost absent in sunspots at different locations (at heliocentric angles of up to 49 • ) on the solar disk. In the sunspot plume, the Lyman lines are also not reversed, whilst the lower Lyman line profiles observed in the plage region are obviously reversed, a phenomenon found also in the normal quiet Sun. The TR densities of the umbra and plume are similar and one order of magnitude lower than those of the plage and penumbra. The DEM curve of the sunspot plume exhibits a peak centered at log(T/K) ∼ 5.45, which exceeds the DEM of other regions by one to two orders of magnitude at these temperatures. We also find that more than 100 lines, which are very weak or not observed anywhere else on the Sun, are well observed by SUMER in the sunspot, especially in the sunspot plume. Conclusions. We suggest that the TR above sunspots is higher and probably more extended, and that the opacity of the hydrogen lines is much lower above sunspots, compared to the TR above plage regions. Our result indicates that the enhanced TR emission of the sunspot plume is probably caused by a large filling factor. The strongly enhanced emission at TR temperatures and the reduced continuum ensure that many normally weak TR lines are clearly distinctive in the spectra of sunspot plumes.

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Section: Hydrogen Lyman Line Profilesmentioning

confidence: 82%

Section: Hydrogen Lyman Line Profilesmentioning

confidence: 99%

Solar transition region above sunspots

Curdt

Teriaca

Landi

et al. 2009

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“…High resolution Lyα and Lyβ profiles measured across the solar disk were published by Curdt et al (2009) and Tian et al (2009b). The Lyα/Lyβ line ratios obtained in these two papers were very high (130-200) and we reanalyze these data using another method to verify the ratio values.…”

Section: Introductionmentioning

confidence: 96%

The solar hydrogen Lymanαto Lymanβline ratio

Lemaire

Vial

Curdt

et al. 2012

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Aims. We investigate the variation in the solar hydrogen Lyman α (Lyα) to Lyman β (Lyβ) line ratio as a function of the solar activity by taking into account new results obtained by SoHO/SUMER and TIMED/SEE. Methods. We reanalyze data of quiet and active regions previously collected with the LPSP multichannel instrument on OSO8. We then re-examine data obtained on the solar disk with SUMER and compare them with previous data. In a second step, we use the full Sun H i Lyβ profiles to determine the Lyβ contribution to the SEE profiles obtained with a 0.4 nm full width at half-maximum. The variation in the Lyα to Lyβ line ratio is then measured for part of the solar cycle 23 (2002-2008). Results. We determine the radiance line ratio of the solar H i Lyα to Lyβ line for a quiet Sun area and the relation between the ratio of the Lyα to Lyβ irradiance and the Lyα solar irradiance.

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“…The obtained genuine Ly-α profiles in the quiet Sun and coronal hole regions were analyzed by Curdt et al (2008), Tian et al (2009a), and Tian et al (2009b). Here we present the first unprecedented Ly-α observations of two quiescent prominences seen in June 2009 and discuss the results from a detailed analysis of the line profiles.…”

Section: Observationsmentioning

confidence: 99%

“…Among other parameters the reversal is related to the amount of neutral hydrogen in its ground state, which by itself is a complex function of the temperature and density structure of the emitting plasma. In addition, flows of the emitting or the absorbing plasma and magnetic field may modulate the sizes of the red or the blue peak and the symmetry of the profile (Curdt et al 2008;Tian et al 2009a).…”

Section: Introductionmentioning

confidence: 99%

The SUMER Ly-α line profile in quiescent prominences

Curdt¹,

Teriaca²,

Schühle³

2010

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Aims. As the result of a novel observing technique, we publish for the first time SoHO-SUMER observations of the true spectral line profile of hydrogen Lyman-α in quiescent prominences. Because SoHO is not in Earth orbit, our high-quality data set is free of geocoronal absorption. We studied the line profile to complement earlier observations of the higher Lyman lines and to substantiate recent model predictions.Methods. We applied the reduced-aperture observing mode to two prominence targets and did a statistical analysis of the line profiles in both data sets. In particular, we investigated the shape of the profile, the radiance distribution, and the line shape-to-radiance interrelation. We also compared Ly-α data to co-temporal λ 1206 Si iii data.Results. We find that the average profile of Ly-α has a blue-peak dominance and is reversed more if the line-of-sight is perpendicular to the field lines. The contrast of Ly-α prominence emission rasters is very low, and the radiance distribution differs from the lognormal distribution of the disk. Features in the Si iii line are not always co-spatial with Ly-α emission.Conclusions. Our empirical results support recent multi-thread models, which predict that asymmetries and depths of the self-reversal depend on the orientation of the prominence axis relative to the line-of-sight.

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Hydrogen Lyman-α and Lyman-β spectral radiance profiles in the quiet Sun

Cited by 33 publications

References 37 publications

Solar transition region above sunspots

Solar transition region above sunspots

The solar hydrogen Lymanαto Lymanβline ratio

The SUMER Ly-α line profile in quiescent prominences

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