Solar polarimetry in the near UV with the Zurich Imaging Polarimeter ZIMPOL II

Gandorfer, A.; Povel, H.P.; Steiner, P.; Aebersold, F.; Egger, U.; Feller, A.; Gisler, D.; Hagenbuch, Stephan; Stenflo, J. O.

doi:10.1051/0004-6361:20040254

Cited by 98 publications

(77 citation statements)

References 13 publications

(15 reference statements)

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“…This highlights the importance of instruments that have simultaneous imaging and spectroscopic capabilities, such as the Meudon/MSDP spectrograph or for example the Bialkow/MSDP spectrograph (Rompolt et al 1994), 2D imaging spectro-polarimeter ZIMPOL II (Zurich Imaging Polarimeter, Gandorfer et al 2004), andIBIS (Interferometric BIdimensional Spectrometer, Cavallini 2006) at Dunn Solar Telescope of the National Solar Observatory. A new-generation MSDP spectrograph is also planned for the EST (European Solar Telescope).…”

Section: Discussionmentioning

confidence: 99%

Dynamics of quiescent prominence fine structures analyzed by 2D non-LTE modelling of the Hα line

Gunár

Mein

Schmieder

et al. 2012

A&A

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Aims. We analyze the dynamics of the prominence fine structures of a quiescent prominence observed on April 26, 2007 during a coordinated campaign of several spaceborne and ground-based instruments. We use Lyman spectra observed by SOHO/SUMER and the Hα line spectra obtained by MSDP spectrograph working at the Meudon Solar Tower. Methods. We employ the 2D multi-thread prominence fine-structure modelling that includes randomly distributed line-of-sight (LOS) velocities of individual threads to derive models producing synthetic Lyman lines in good agreement with the SOHO/SUMER observations. We then use these models to produce synthetic Hα line spectra that we compare with the observed spectra using three statistical parameters: the line integrated intensity, the line full-width at half-maximum (FWHM), and the Doppler velocity derived from shifts of the line profiles. Results. We demonstrate that the 2D multi-thread models that produce synthetic Lyman spectra in agreement with observations also generate synthetic Hα spectra in good agreement with the observed ones. The statistical analysis of the FWHM and Doppler velocities of the synthetic Hα line profiles show that the overall LOS velocities in the April 26, 2007 prominence at the time of the observations were below 15 km s −1 and in the prominence core were close to 10 km s −1 . In combination with the analysis of the Lyman spectra, we determine several physical parameters of the observed prominence fine-structures that show that the April 26, 2007 prominence had a relatively low-mass weakly magnetized structure. We are also able to impose some constraints on the prominence core temperature, which may be relatively low, with values below 6000 K. Conclusions. The combination of 2D non-LTE prominence fine-structure modelling with the statistical analysis of the observed and synthetic Lyman and Hα spectra allows us to analyze the influence of the model input parameters and the velocity fields on the synthetic Hα line profiles, thus determine the overall dynamics of the observed prominence as well as the physical parameters of its plasma.

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Section: Discussionmentioning

confidence: 99%

Dynamics of quiescent prominence fine structures analyzed by 2D non-LTE modelling of the Hα line

Gunár

Mein

Schmieder

et al. 2012

A&A

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“…At the measurement wavelength of 633 nm, the rms wavefront error in double pass including the autocollimation sphere and the interferometer was λ/22. Polarimetric properties of the ISLiD-IMaX feed path were characterized in terms of Mueller matrix maps over the full IMaX field of view by inserting polarization optics (rotatable linear polarizer and quarter wave plate) in front of F2 and measuring the full Stokes vector image at F4 with the Zurich imaging polarimeter ZIMPOL II (Gandorfer et al, 2004) at a wavelength of 525 nm selected by an interference filter of 5 nm width.…”

Section: Optical On-ground Performancementioning

confidence: 99%

The Filter Imager SuFI and the Image Stabilization and Light Distribution System ISLiD of the Sunrise Balloon-Borne Observatory: Instrument Description

et al. 2010

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We describe the design of the Sunrise Filter Imager (SuFI) and the Image Stabilization and Light Distribution (ISLiD) unit onboard the Sunrise balloon borne solar observatory. This contribution provides the necessary information which is relevant to understand the instruments' working principles, the relevant technical data, and the necessary information about calibration issues directly related to the science data.

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“…Every two to three weeks, measurements of scattering polarization are taken in several selected wavelength regions, namely C 2 5141 Å, Cr i 5206 Å and Fe i 4383 Å at several position angles around the solar limb (N, NW, W, SW, S) near a heliocentric angle μ = cos θ = 0.1 (5 from the limb) and with a slit of 0.5 width and 180 length. The observations are carried out with the UV sensitive ZIMPOL2 system (Gandorfer et al 2004;Kleint et al 2008) and the high-resolution spectrograph at the 45 cm telescope of the Istituto Ricerche Solari Locarno (IRSOL). The integration time of about 15 min is enough to achieve the sensitivity of 10 −5 , but together with telescope and camera overheads and calibrations each measurement for one single position angle and wavelength takes about 45 min.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Solar turbulent magnetic fields: surprisingly homogeneous distribution during the solar minimum

Kleint

Berdyugina

Шапиро

et al. 2010

A&A

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Context. Small-scale, weak magnetic fields are ubiquitous in the quiet solar atmosphere. Yet their properties and temporal and spatial variations are not well known. Aims. We have initiated a synoptic program, carried out at the Istituto Ricerche Solari Locarno (IRSOL), to investigate both turbulent, mixed-polarity magnetic fields and nearly horizontal, directed fields and their variation with the solar cycle. Methods. Through spectropolarimetric observations we monitor linear and circular polarization at the solar limb (5 on the disk) at five positional angles (N, NW, S, SW, W) with the sensitivity of ∼10 −5 . In addition, we analyzed measurements taken at different limb distances. We measure signatures in the 5141 Å region including two C 2 triplets and three Fe i lines. Linear polarization in these lines arises from scattering and can be modified via the Hanle effect in the presence of turbulent magnetic fields. Through the application of the differential Hanle effect to the C 2 R-triplet line ratios and the use of a simplified line formation model, we are able to infer a strength of turbulent magnetic fields while using the P-triplet to further restrict it. A Zeeman analysis of Fe i Stokes V/I is used to evaluate flux densities of horizontally directed fields. Results. We conclude that weak fields were evenly distributed over the Sun during this solar minimum. The turbulent field strength was at least 4.7 ± 0.2 G, and it did not vary during the last two years. This result was complemented with earlier, mainly unpublished measurements in the same region, which extend our set to nearly one decade. A statistical analysis of these all data suggests that there could be a very small variation of the turbulent field strength (3σ-limit) since the solar maximum in 2000. The Zeeman analysis of Fe i Stokes V/I reveals weak horizontal flux densities of 3-8 G.Conclusions. Our results demonstrate the potential of long-term observations of small-scale magnetic fields, which may vary with the solar cycle in both mean strength and spatial distribution. This provides important constraints on the energy budget of the solar cycle. Extending this synoptic program to many spectral lines would provide a sample of heights in the solar atmosphere.

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Solar polarimetry in the near UV with the Zurich Imaging Polarimeter ZIMPOL II

Cited by 98 publications

References 13 publications

Dynamics of quiescent prominence fine structures analyzed by 2D non-LTE modelling of the Hα line

Dynamics of quiescent prominence fine structures analyzed by 2D non-LTE modelling of the Hα line

The Filter Imager SuFI and the Image Stabilization and Light Distribution System ISLiD of the Sunrise Balloon-Borne Observatory: Instrument Description

Solar turbulent magnetic fields: surprisingly homogeneous distribution during the solar minimum

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