Thomson Scattering above Solar Active Regions and an Ad Hoc Polarization Correction Method for the Emissive Corona

Schad, Thomas A.; Jaeggli, Sarah A.; Dima, Gabriel I.

doi:10.3847/1538-4357/ac713c

Cited by 3 publications

(2 citation statements)

References 39 publications

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“…We first show forward synthesized images of the polarized brightness due to the Thomson-scattered K-corona for both PSI-MAS models using the methods outlined by Schad et al (2022) (see panels (b) and (c) of Figure 9). These images are useful for comparing the large-scale topology of the off-limb corona with observations.…”

Section: Polarized Brightness Of Thomson Scatteringmentioning

confidence: 99%

First Infrared Coronal Spectra from DKIST/Cryo-NIRSP: Comparisons with Global MHD Models

Schad

Kuhn

Fehlmann

et al. 2023

ApJ

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The Cryogenic Near-Infrared Spectropolarimeter (Cryo-NIRSP) is now conducting science operations at the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST). We report results obtained during instrument commissioning that advance multiwavelength coronagraphic observations in the infrared. This includes the first observations of the Fe xiii 1075 nm, Fe xiii 1079 nm, Si x 1430 nm, and Si ix 3934 nm forbidden lines. The Si ix observations, in particular, significantly improve upon the few previous ground-based detections and open up this diagnostic for more routine study. We analyse long-slit spectra in each line sampling elongations from 1.06 to 1.52 solar radii above the northeast solar limb on 2022 February 14. Line characteristics as a function of radial distance are derived and discussed in comparison to modeled emission emergent from global coronal magnetohydrodynamic models with different heating prescriptions. We find favorable correspondence between the observations and different aspects of these models, and further demonstrate the utility of infrared observations for constraining coronal models. Continued DKIST/Cryo-NIRSP observations including polarimetric data, together with ongoing improvements in data calibrations, promise significant value for coronal studies.

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Section: Polarized Brightness Of Thomson Scatteringmentioning

confidence: 99%

First Infrared Coronal Spectra from DKIST/Cryo-NIRSP: Comparisons with Global MHD Models

Schad

Kuhn

Fehlmann

et al. 2023

ApJ

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show abstract

“…These advances represent a significant step forward for observations of this line, and they lend further support for advancing polarized observations in this bandpass in pursuit of magnetic field diagnostics. Well-calibrated polarimetric observations may also aid in the separation of the multiple solar and telluric signals that contribute to the observed flux due to the unique conditions that polarize these components (see, e.g., Schad et al 2022). We show its deviation from the best fit in units of picometers.…”

Section: Discussionmentioning

confidence: 95%

Coronagraphic Observations of Si x 1430 nm Acquired by DKIST/Cryo-NIRSP with Methods for Telluric Absorption Correction

Schad,

Fehlmann,

Dima

et al. 2024

ApJ

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We report commissioning observations of the Si x 1430 nm solar coronal line observed coronagraphically with the Cryogenic Near-Infrared Spectropolarimeter at the National Science Foundation’s Daniel K. Inouye Solar Telescope. These are the first known spatially resolved observations of this spectral line, which has strong potential as a coronal magnetic field diagnostic. The observations target a complex active region located on the solar northeast limb on 2022 March 4. We present a first analysis of these data that extracts the spectral line properties through a careful treatment of the variable atmospheric transmission that is known to impact this spectral window. Rastered images are created and compared with extreme-UV observations from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) instrument. A method for estimating the electron density from the Si x observations is then demonstrated that makes use of the forbidden line density-sensitive emissivity and an emission-measure analysis of the SDO/AIA bandpass observations. In addition, we derive an effective temperature and nonthermal line width across the region. This study informs the calibration approaches required for more routine observations of this promising diagnostic line.

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Systems Approach to Polarization Calibration for the Daniel K. Inouye Solar Telescope (DKIST)

et al. 2023

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The Daniel K. Inouye Solar Telescope (DKIST) advances studies of solar magnetism through high-precision and accuracy in polarimetry at frontier spatial and temporal scales. A system model for polarization response in azimuth and altitude has been developed to calibrate DKIST instruments. The DKIST team has developed several new modeling and performance-estimation techniques coupled with thorough metrology. These efforts ensure that quality polarimetry is delivered to meet stringent accuracy requirements. A custom spectropolarimetric calibration system was designed, installed, and used to perform end-to-end calibration of the telescope using the beam within the Cryo-NIRSP instrument. Extensive optical and polarization characterization efforts allow for the reduction of systematic errors within a detailed system model that includes elliptical calibration retarders. Coating witness samples for every relevant optic in the system have been measured. Aperture-dependent variations in polarizer, retarder, and optic-coating performance have been measured and used to simulate both the polarization dependence on field angle and errors within the optical-system model. Multiple observations on-Sun and with a calibration lamp agree well with each other and with the system model. Upcoming multi-instrument observations are expected to be well calibrated with detailed understanding of major error limitations.

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Thomson Scattering above Solar Active Regions and an Ad Hoc Polarization Correction Method for the Emissive Corona

Cited by 3 publications

References 39 publications

First Infrared Coronal Spectra from DKIST/Cryo-NIRSP: Comparisons with Global MHD Models

First Infrared Coronal Spectra from DKIST/Cryo-NIRSP: Comparisons with Global MHD Models

Coronagraphic Observations of Si x 1430 nm Acquired by DKIST/Cryo-NIRSP with Methods for Telluric Absorption Correction

Systems Approach to Polarization Calibration for the Daniel K. Inouye Solar Telescope (DKIST)

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