Hopes and expectations with GREGOR

Kneer, F.

doi:10.1002/asna.201211726

Cited by 8 publications

(8 citation statements)

References 18 publications

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“…Both emission peaks are much wider than the typical H 2v and H 2r emission peaks in a quiet Sun profile, with a FWHM of about 50-100 pm compared to a typical width of 25 pm in the average quiet Sun profile. This is also in contrast to typical plage profiles (e.g., Linsky & Avrett 1970;Kneer 2010) where both emission peaks are comparably elevated and the H 3 minimum is shallower than in a quiet Sun profile. The distance between the H 2 emission peaks as well as H 1 minima is much larger than in a typical quiet Sun profile (rightmost panel of middle row, Fig.…”

Section: Spectral Line Profilescontrasting

confidence: 86%

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Multiwavelength spectropolarimetric observations of an Ellerman bomb

Rezaei

Beck

2015

A&A

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Context. Ellerman bombs (EBs) are enhanced emission in the wings of the Hα line in the solar spectrum. Aims. We study the structure of an EB in the photosphere and chromosphere.Methods. We analyze simultaneous observations of four chromospheric lines (Hα, Ca ii H, Ca ii IR 854 nm, and He i 1083 nm) as well as two photospheric lines (Fe i 630 and Si i 1082.7 nm) along with high-cadence 160 and 170 nm ultraviolet (UV) continuum filtergrams. Full Stokes data from the Helioseismic and Magnetic Imager (HMI) are used to trace the temporal evolution of the magnetic structure.Results. We identify the EB by excess emission in the wings of the Hα line, a brightening in the UV continuum, and large emission peaks in the core of the two Ca ii lines. The EB shows a blueshift in all chromospheric lines, while no shifts are observed in the photospheric lines. The blueshift in the chromospheric layer causes very asymmetric emission peaks in the Ca ii H line. The photospheric Si i spectral line shows a shallower line depth at the location of the EB. The UV continuum maps show that the EB was substantially brighter than its surroundings for about 30 min. The continuum contrast of the EB from 170 nm to 1080 nm shows a power-law dependency on the wavelength. The temperature enhancement amounts to 130 K in the low photosphere and 400 K at the temperature minimum level. This temperature excess is also seen in an LTE inversion of the Ca ii spectra. The total thermal and radiative energy content of the EB is about 10 20 J and 10 18 J in the photosphere and chromosphere, respectively. The HMI data hints at a photospheric magnetic flux cancellation as the driver of the EB. Conclusions. Ellerman bombs release the energy in a height range of several pressure scale heights around the temperature minimum such that they affect both the photosphere and the lower chromosphere.

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Section: Spectral Line Profilescontrasting

confidence: 86%

“…The brightening peaks at about Hα ± 1.2 Å and fades away toward ±5 Å (Berlicki et al 2010;Kneer 2010). This excess emission corresponds to a temperature enhancement of 600 to 2000 K at about the height of the temperature minimum (Georgoulis et al 2002;Fang et al 2006;Hong et al 2014).…”

Section: Introductionmentioning

confidence: 89%

Multiwavelength spectropolarimetric observations of an Ellerman bomb

Rezaei

Beck

2015

A&A

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“…3.5.3 above. The enhanced intensity of the line wings close to the Ca II H core resembles closely the well-known mustache phenomenon seen in Hα or Hβ (Severny 1956;Kneer 2010). Mustaches are observed in active regions or network boundaries, whereas our observations are made in inter-network regions of very quiet Sun.…”

Section: Comparison With Other Linessupporting

confidence: 83%

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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“…The EFR/AFS was observed with GRIS at the 1.5-meter GREGOR solar telescope (Denker et al 2012, Kneer 2012 on 2015 April 17 as part of a coordinated observing campaign. González Manrique et al (2016) described preliminary results of fitting dual-component He i 10830Å spectral profiles.…”

Section: Observationsmentioning

confidence: 99%

Flows along arch filaments observed in the GRIS ‘very fast spectroscopic mode’

et al. 2016

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A new generation of solar instruments provides improved spectral, spatial, and temporal resolution, thus facilitating a better understanding of dynamic processes on the Sun. High-resolution observations often reveal multiple-component spectral line profiles, e.g., in the near-infrared He i 10830 Å triplet, which provides information about the chromospheric velocity and magnetic fine structure. We observed an emerging flux region, including two small pores and an arch filament system, on 2015 April 17 with the ‘very fast spectroscopic mode’ of the GREGOR Infrared Spectrograph (GRIS) situated at the 1.5-meter GREGOR solar telescope at Observatorio del Teide, Tenerife, Spain. We discuss this method of obtaining fast (one per minute) spectral scans of the solar surface and its potential to follow dynamic processes on the Sun. We demonstrate the performance of the ‘very fast spectroscopic mode’ by tracking chromospheric high-velocity features in the arch filament system.

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Hopes and expectations with GREGOR

Cited by 8 publications

References 18 publications

Multiwavelength spectropolarimetric observations of an Ellerman bomb

Multiwavelength spectropolarimetric observations of an Ellerman bomb

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

Flows along arch filaments observed in the GRIS ‘very fast spectroscopic mode’

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