Polarisationsinterferenzfilter und ihre Prüfung( Mitteilungen des Astrophysikalischen Observatoriums Potsdam Nr.43)

Künzel, Heike

doi:10.1002/asna.19552820604

Cited by 4 publications

(4 citation statements)

References 2 publications

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“…The Hα interference filter acts in this case as an order-sorting filter for the Lyot filter. The narrow-band (Δλ=60 pm) Hα filtergrams are obtained with a Lyot filter manufactured in 1945 and modified later by Bernhard Halle Nachf., Berlin-Steglitz 33 . The Halle filter No.…”

Section: Optical Designmentioning

confidence: 99%

“…The narrow-band (Δλ ¼ 60 pm) Hα filtergrams are obtained with a Lyot filter manufactured in 1945 and modified later by Bernhard Halle Nachf., Berlin-Steglitz. 33 The Halle filter No. 22 was originally located at the solar observatory Einstein Tower 34 but was transferred to Observatorio del Teide for high-resolution imaging.…”

Section: Dual-channel Design Of the Imagermentioning

confidence: 99%

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Improved High-resolution Fast Imager

Denker

Verma

Wiśniewska

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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The improved High-resolution Fast Imager (HiFI+) is a multiwavelength imaging filtergraph, which was commissioned at the GREGOR solar telescope at Observatorio del Teide, Izaña, Tenerife, Spain, in March 2022followed by science verification in April 2022, after which it entered routine observations. Three camera control computers with two synchronized sCMOS and CMOS cameras each provide near diffraction-limited imaging at high cadence in six wavelength bands (Ca II H at 396.8 nm, G-band at 430.7 nm, blue continuum at 450.6 nm, narrow-and broad-band Hα at 656.3 nm, and TiO bandhead at 705.8 nm). This unique combination of photospheric and chromospheric images provides "tomographic" access to the dynamic Sun and complements spectropolarimetric observations at the GREGOR telescope. High image acquisition rates of 50 and 100 Hz facilitate image restoration, where time series of restored images have a typical cadence of 6 and 12 s, which is sufficient to resolve the dynamics of the solar photosphere and chromosphere. In principle, all imaging channels can be restored individually using the speckle masking technique or multiframe blind deconvolution (MFBD). However, images recorded strictly simultaneously in the narrow-/broad-band Hα and the G-band/blue continuum channels can be pairwise subjected to multiobject multiframe deconvolution (MOMFBD) expanding the science capabilities of HiFI+. For example, the narrowband (FWHM = 60 nm) Halle Hα Lyot filter isolates the Hα line core, which facilitates matching chromospheric fibrils and filamentary structures to photospheric bright points. Likewise, dividing G-band by blue continuum images enhances small-scale brightenings, which are often related to small-scale magnetic fields so that their evolution can be tracked in time. A detailed description of the improved high-cadence, large-format imaging system is presented and its performance is assessed based on first-light observations.

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Section: Optical Designmentioning

confidence: 99%

Section: Dual-channel Design Of the Imagermentioning

confidence: 99%

Improved High-resolution Fast Imager

Denker

Verma

Wiśniewska

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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“…As an alternative to observations with the echelle spectrograph, a system of two synchronized LaVision Imager M-lite 2M CMOS cameras were used to capture narrow-and broadband Hα filtergrams. The narrowband filtergrams were obtained with a Lyot filter (λ6562.8 Å and ∆λ = 0.60 Å) manufactured by Bernhard Halle Nachf., Berlin-Steglitz (Künzel 1955), and the broadband filtergrams were captured with an interference filter (λ6567 Å and ∆λ = 7.5 Å). The details about the setup and data processing are given in Denker et al (2020).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

High-resolution spectroscopy of a surge in an emerging flux region

Verma

Denker

Diercke

et al. 2020

A&A

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Aims. The regular pattern of quiet-Sun magnetic fields was disturbed by newly emerging magnetic flux, which led a day later to two homologous surges after renewed flux emergence, affecting all atmospheric layers. Hence, simultaneous observations in different atmospheric heights are needed to understand the interaction of rising flux tubes with the surrounding plasma, in particular by exploiting the important diagnostic capabilities provided by the strong chromospheric Hα line regarding morphology and energetic processes in active regions. Methods. A newly emerged active region NOAA 12722 was observed with the Vacuum Tower Telescope (VTT) at Observatorio del Teide, Tenerife, Spain, on 11 September 2018. High spectral resolution observations using the echelle spectrograph in the chromospheric Hαλ6562.8 Å line were obtained in the early growth phase. Noise-stripped Hα line profiles yield maps of line-core and bisector velocities, which were contrasted with velocities inferred from Cloud Model inversions. A high-resolution imaging system recorded simultaneously broad- and narrowband Hα context images. The Solar Dynamics Observatory provided additional continuum images, line-of-sight (LOS) magnetograms, and UV and extreme UV (EUV) images, which link the different solar atmospheric layers. Results. The active region started as a bipolar region with continuous flux emergence when a new flux system emerged in the leading part during the VTT observations, resulting in two homologous surges. While flux cancellation at the base of the surges provided the energy for ejecting the cool plasma, strong proper motions of the leading pores changed the magnetic field topology making the region susceptible to surging. Despite the surge activity in the leading part, an arch filament system in the trailing part of the old flux remained stable. Thus, stable and violently expelled mass-loaded ascending magnetic structures can coexist in close proximity. Investigating the height dependence of LOS velocities revealed the existence of neighboring strong up- and downflows. However, downflows occur with a time lag. The opacity of the ejected cool plasma decreases with distance from the base of the surge, while the speed of the ejecta increases. The location at which the surge becomes invisible in Hα corresponds to the interface where the surge brightens in He IIλ304 Å. Broad-shouldered and dual-lobed Hα profiles suggests accelerated or decelerated and highly structured LOS plasma flows. Significantly broadened Hα profiles imply significant heating at the base of the surges, which is also supported by bright kernels in UV and EUV images uncovered by swaying motions of dark fibrils at the base of the surges. Conclusions. The interaction of newly emerging flux with pre-existing flux concentrations of a young, diffuse active region provided suitable conditions for two homologous surges. High-resolution spectroscopy revealed broadened and dual-lobed Hα profiles tracing accelerated or decelerated flows of cool plasma along the multi-threaded structure of the surge.

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“…As an alternative to observations with the echelle spectrograph, a system of two synchronized LaVision Imager M-lite 2M CMOS cameras were used to capture narrow-and broadband Hα filtergrams. The narrow-band filtergrams were obtained with a Lyot filter (λ6562.8 Å and ∆λ = 0.60 Å) manufactured by Bernhard Halle Nachf., Berlin-Steglitz (Künzel 1955), and the broad-band filtergrams were captured with an interference filter (λ6567 Å and ∆λ = 7.5 Å). The details about setup and data processing are given in Denker et al (2020).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

High-resolution spectroscopy of a surge in an emerging flux region

Verma,

Denker,

Diercke

et al. 2020

Preprint

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Aims. The regular pattern of quiet-Sun magnetic fields was disturbed by newly emerging magnetic flux, which led a day later to two homologous surges after renewed flux emergence, affecting all atmospheric layers. Hence, simultaneous observations in different atmospheric heights are needed to understand the interaction of rising flux tubes with the surrounding plasma, in particular by exploiting the important diagnostic capabilities provided by the strong chromospheric Hα line regarding morphology and energetic processes in active regions. Methods. A newly emerged active region NOAA 12722 was observed with the Vacuum Tower Telescope (VTT) at Observatorio del Teide, Tenerife, Spain on 11 September 2018. High-spectral resolution observations using the echelle spectrograph in the chromospheric Hα λ6562.8 Å line were obtained in the early growth phase. Noise-stripped Hα line profiles yield maps of line-core and bisector velocities, which were contrasted with velocities inferred from Cloud Model inversions. A high-resolution imaging system recorded simultaneously broad-and narrow-band Hα context images. The Solar Dynamics Observatory (SDO) provided additional continuum images, line-of-sight (LOS) magnetograms, and UV/EUV images, which link the different solar atmospheric layers.Results. The active region started as a bipolar region with continuous flux emergence when a new flux system emerged in the leading part during the VTT observations, resulting in two homologous surges. While flux cancellation at the base of the surges provided the energy for ejecting the cool plasma, strong proper motions of the leading pores changed the magnetic field topology making the region susceptible for surging. Despite the surge activity in the leading part, an arch filament system in the trailing part of the old flux remained stable. Thus, stable and violently expelled mass-loaded ascending magnetic structures can co-exist in close proximity. Investigating the height dependence of LOS velocities revealed the existence of neighboring strong up-and downflows. However, downflows occur with a time lag. The opacity of the ejected cool plasma decreases with distance from the base of the surge while the speed of the ejecta increases. The location at which the surge becomes invisible in Hα corresponds to the interface where the surge brightens in He ii λ304 Å. Broad-shoulders and dual-lobed Hα profiles suggests accelerated/decelerated and highly structured LOS plasma flows. Significantly broadened Hα profiles imply significant heating at the base of the surges, which is also supported by bright kernels in UV/EUV images uncovered by swaying motions of dark fibrils at the base of the surges. Conclusions. The interaction of newly emerging flux with pre-existing flux concentrations of a young, diffuse active region provided suitable conditions for two homologous surges. High-resolution spectroscopy revealed broadened and dual-lobed Hα profiles tracing accelerated/decelerated flows of cool plasma along the multi-threaded structure of the surge.

show abstract

Polarisationsinterferenzfilter und ihre Prüfung( Mitteilungen des Astrophysikalischen Observatoriums Potsdam Nr.43)

Cited by 4 publications

References 2 publications

Improved High-resolution Fast Imager

Improved High-resolution Fast Imager

High-resolution spectroscopy of a surge in an emerging flux region

High-resolution spectroscopy of a surge in an emerging flux region

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