The energy of waves in the photosphere and lower chromosphere

Beck, C.; Rezaei, Reza; Puschmann, K. G.

doi:10.1051/0004-6361/201220463

Cited by 26 publications

(27 citation statements)

References 142 publications

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“…They report on time differences between subsequent occurrences of 170 to 220 s on average, and three to five repetitions. Their findings concerning the occurrence of bright grains was confirmed by Beck et al (2013b). Figure 10 shows Fe II emission repetitions within 15 to 25 time steps, (corresponding to 120 to 200 s).…”

Section: Comparison With Chromospheric Grains and Supersonic Eventsmentioning

confidence: 60%

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: Comparison With Chromospheric Grains and Supersonic Eventsmentioning

confidence: 60%

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

Schmidt

Fisher

2013

A&A

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“…Figure 11 shows the modulus of the temperature and the relative temperature variations on two spatial cuts across a network element (see also Fig. 16 of Beck et al 2013b). The locations of the cuts are indicated by the white dashed lines in the temperature map at log τ = −5.1 of Fig.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Beck et al (2013b) discussed the match of such NLTE profiles with individual and average observed Ca spectra. These synthetic NLTE profiles were only multiplied with the transmission profile of the 0.3 nm filter (lower panel of Fig.…”

Section: Observations and Creation Of Synthetic Ca Imagesmentioning

confidence: 99%

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Can spicules be detected at disc centre in broad-band Ca ii H filter imaging data?

Beck

Rezaei

Puschmann

2013

A&A

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Context.Recently, a possible identification of type II spicules in broad-band (full-width at half-maximum (FWHM) of ∼0.3 nm) filter imaging data in Ca ii H on the solar disc was reported. Aims. We estimate the formation height range contributing to broad-band and narrow-band filter imaging data in Ca ii H to investigate whether spicules can be detected in such observations at the centre of the solar disc.Methods. We applied spectral filters of FWHMs from 0.03 nm to 1 nm to observed Ca ii H line profiles to simulate Ca imaging data. We used observations across the limb to estimate the relative intensity contributions of off-limb and on-disc structures. We compared the synthetic Ca filter imaging data with intensity maps of Ca spectra at different wavelengths and temperature maps at different optical depths obtained by an inversion of these spectra. In addition, we determined the intensity response function for the wavelengths covered by the filters of different FWHM. Results. In broad-band (FWHM = 0.3 nm) Ca imaging data, the intensity emitted off the solar limb is about 5% of the intensity at disc centre. For a 0.3-nm-wide filter centred at the Ca ii H line core, up to about one third of the off-limb intensity comes from emission in H . On the disc, only about 10 to 15% of the intensity transmitted through a broad-band filter comes from the linecore region between the H 1 minima (396.824 to 396.874 nm). No traces of elongated fibrillar structures are visible in the synthetic Ca broad-band imaging data at disc centre, in contrast to the line-core images of the Ca spectra. The intensity-weighted response function for a 0.3-nm-wide filter centred at the Ca ii H line core peaks at about log τ ∼ −2 (z ∼ 200 km). Relative contributions from atmospheric layers above 800 km are about 10%. The inversion results suggest that the slightly enhanced emission around the photospheric magnetic network in broad-band Ca imaging data is caused by a thermal canopy at a height of about 600 km.Conclusions. Broad-band (∼0.3 nm) Ca ii H imaging data do not trace upper chromospheric structures such as spicules in observations at the solar disc because of the too small relative contribution of the line core to the total wavelength-integrated filter intensity. The faint haze around network elements in broad-band Ca imaging observations at disc centre presumably traces thermal canopies in the vicinity of magnetic flux concentrations instead.

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“…The LTE inversion code finds the best match to an observed profile of a Ca ii line by a comparison to all of the about 240,000 archive spectra and subsequently retrieves the corresponding temperature stratification. Beck et al (2013b), Beck et al (2014) and the Appendix discuss the accuracy that can be achieved in the reproduction of observed profiles.…”

Section: Observationsmentioning

confidence: 99%

FAST INVERSION OF SOLAR Ca II SPECTRA

Beck

Choudhary

Rezaei

et al. 2014

ApJ

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We present a fast (≪ 1 s per profile) inversion code for solar Ca ii lines. The code uses an archive of spectra that are synthesized prior to the inversion under the assumption of local thermodynamic equilibrium (LTE). We show that it can be successfully applied to spectrograph data or more sparsely sampled spectra from two-dimensional spectrometers. From a comparison to a non-LTE inversion of the same set of spectra, we derive a first-order non-LTE correction to the temperature stratifications derived in the LTE approach. The correction factor is close to unity up to log τ ∼ −3 and increases to values of 2.5 and 4 at log τ = −6 in the quiet Sun and the umbra, respectively.

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The energy of waves in the photosphere and lower chromosphere

Cited by 26 publications

References 142 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

Can spicules be detected at disc centre in broad-band Ca ii H filter imaging data?

FAST INVERSION OF SOLAR Ca II SPECTRA

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