The GREGOR adaptive optics system

Berkefeld, T.; Schmidt, Dirk; Soltau, D.; Lühe, O. von der; Heidecke, F.

doi:10.1002/asna.201211739

Cited by 57 publications

(57 citation statements)

References 11 publications

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“…c Values taken from Bloomfield et al (2007) small not to heavily distort the continuum images reconstructed from the individual slit positions. The GREGOR Adaptive Optics System (GAOS; Berkefeld et al 2012) worked throughout the entire scans (see Sections 4.1.2 and 4.2). We note that the Fried parameter r 0 scales as λ 6/5 and therefore the size of the isoplanatic patches is about 2.5 times larger at 1565 nm than at 630 nm, thereby allowing the AO to perform much better (e.g.…”

Section: Gregor'smentioning

confidence: 99%

Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps

Borrero

Ramos

Collados

et al. 2016

A&A

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Context. Some models for the topology of the magnetic field in sunspot penumbrae predict the existence of field-free or dynamically weak-field regions in the deep Photosphere. Aims. To confirm or rule out the existence of weak-field regions in the deepest photospheric layers of the penumbra. Methods. The magnetic field at log τ5 = 0 is investigated by means of inversions of spectropolarimetric data of two different sunspots located very close to disk center with a spatial resolution of approximately 0.4-0.45 ′′ . The data have been recorded using the GRIS instrument attached to the 1.5-meters GREGOR solar telescope at El Teide observatory. It includes three Fe i lines around 1565 nm, whose sensitivity to the magnetic field peaks at half a pressure-scale-height deeper than the sensitivity of the widely used Fe i spectral line pair at 630 nm. Prior to the inversion, the data is corrected for the effects of scattered light using a deconvolution method with several point spread functions. Results. At log τ5 = 0 we find no evidence for the existence of regions with dynamically weak (B < 500 Gauss) magnetic fields in sunspot penumbrae. This result is much more reliable than previous investigations done with Fe i lines at 630 nm. Moreover, the result is independent of the number of nodes employed in the inversion, and also independent of the point spread function used to deconvolve the data, and does not depend on the amount of straylight (i.e. wide-angle scattered light) considered.

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Section: Gregor'smentioning

confidence: 99%

Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps

Borrero

Ramos

Collados

et al. 2016

A&A

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“…It is built on the experience from the earlier experiments at the VTT and the DST. We use the AO control software KAOS, which was originally developed for the GRE-GOR telescope (Berkefeld et al 2012), because we can easily adapt and extend it for our experiments. Clear features three identical 357-actuator DMs, two of which are dedicated to highaltitude seeing, and the third always being located in a pupil image.…”

Section: Clear the Solar Mcao Pathfinder On The Nstmentioning

confidence: 99%

Clearwidens the field for observations of the Sun with multi-conjugate adaptive optics

Schmidt

Gorceix

Goode

et al. 2017

A&A

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The multi-conjugate adaptive optics (MCAO) pathfinder Clear on the New Solar Telescope in Big Bear Lake has provided the first-ever MCAO-corrected observations of the Sun that show a clearly and visibly widened corrected field of view compared to quasisimultaneous observations with classical adaptive optics (CAO) correction. Clear simultaneously uses three deformable mirrors, each conjugated to a different altitude, to compensate for atmospheric turbulence. While the MCAO correction was most effective over an angle that is approximately three times wider than the angle that was corrected by CAO, the full 53 field of view did benefit from MCAO correction. We further demonstrate that ground-layer-only correction is attractive for solar observations as a complementary flavor of adaptive optics for observational programs that require homogenous seeing improvement over a wide field rather than diffraction-limited resolution. We show illustrative images of solar granulation and of a sunspot obtained on different days in July 2016, and present a brief quantitative analysis of the generalized Fried parameters of the images.

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“…2.2). The GREGOR adaptive optics system (GAOS, Berkefeld et al 2012) was performing well during the acquisition of the data. Polarimetric calibration as well as dark and flat-field corrections were applied following the standard procedures described in Collados (1999Collados ( , 2003.…”

Section: Data Setmentioning

confidence: 99%

Signatures of the impact of flare-ejected plasma on the photosphere of a sunspot light bridge

Felipe

Collados

Khomenko

et al. 2017

A&A

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Aims. We investigate the properties of a sunspot light-bridge, focusing on the changes produced by the impact of a plasma blob ejected from a C-class flare. Methods. We observed a sunspot in active region NOAA 12544 using spectropolarimetric raster maps of the four Fe i lines around 15655 Å with the GREGOR Infrared Spectrograph (GRIS), narrow-band intensity images sampling the Fe i 6173 Å line with the GREGOR Fabry-Pérot Interferometer (GFPI), and intensity broad band images in G-band and Ca ii H band with the High-resolution Fast Imager (HiFI). All these instruments are located at the GREGOR telescope at the Observatorio del Teide, Tenerife, Spain. The data cover the time before, during, and after the flare event. The analysis is complemented with Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) data from the Solar Dynamics Observatory (SDO). The physical parameters of the atmosphere at differents heights were inferred using spectral-line inversion techniques. Results. We identify photospheric and chromospheric brightenings, heating events, and changes in the Stokes profiles associated to the flare eruption and the subsequent arrival of the plasma blob to the light bridge, after traveling along an active region loop. Conclusions. The measurements suggest that these phenomena are the result of reconnection events driven by the interaction of the plasma blob with the magnetic field topology of the light bridge.

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The GREGOR adaptive optics system

Cited by 57 publications

References 11 publications

Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps

Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps

Clearwidens the field for observations of the Sun with multi-conjugate adaptive optics

Signatures of the impact of flare-ejected plasma on the photosphere of a sunspot light bridge

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