The Airborne Infrared Spectrometer (AIR-Spec) was commissioned during the 2017 total solar eclipse, when it observed five infrared coronal emission lines from a Gulfstream V research jet owned by the National Science Foundation and operated by the National Center for Atmospheric Research. The second AIR-Spec research flight took place during the 2019 July 2 total solar eclipse across the south Pacific. The 2019 eclipse flight resulted in seven minutes of observations, during which the instrument measured all four of its target emission lines: S
The Airborne Infrared Spectrometer (AIR-Spec) offers an unprecedented opportunity to explore the near-infrared (NIR) wavelength range. It has been flown at two total solar eclipses, in 2017 and 2019. The wavelength range of the much-improved instrument on the second flight (2019 July 2) was shifted to cover two density-sensitive lines from S
- NSF-PAR ID:
- 10398183
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal Supplement Series
- Volume:
- 265
- Issue:
- 1
- ISSN:
- 0067-0049
- Format(s):
- Medium: X Size: Article No. 11
- Size(s):
- ["Article No. 11"]
- Sponsoring Org:
- National Science Foundation
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Abstract xi 1.393μ m, Six 1.431μ m, Sxi 1.921μ m, and Feix 2.853μ m. The 1.393μ m Sxi line was detected for the first time, and probable first detections were made of Sixi 1.934μ m and Fex 1.947μ m. The 2017 AIR-Spec detection of Feix was confirmed and the first observations were made of the Feix line intensity as a function of solar radius. Telluric absorption features were used to calibrate the wavelength mapping, instrumental broadening, and throughput of the instrument. AIR-Spec underwent significant upgrades in preparation for the 2019 eclipse observation. The thermal background was reduced by a factor of 30, providing a 5.5× improvement in signal-to-noise ratio, and the postprocessed pointing stability was improved by a factor of 5 to <10″ rms. In addition, two imaging artifacts were identified and resolved, improving the spectral resolution and making the 2019 data easier to interpret. -
Abstract Differential emission measure (DEM) inversion methods use the brightness of a set of emission lines to infer the line-of-sight (LOS) distribution of the electron temperature (
T e ) in the corona. DEM inversions have been traditionally performed with collisionally excited lines at wavelengths in the extreme ultraviolet and X-ray. However, such emission is difficult to observe beyond the inner corona (1.5R ⊙), particularly in coronal holes. Given the importance of theT e distribution in the corona for exploring the viability of different heating processes, we introduce an analog of the DEM specifically for radiatively excited coronal emission lines, such as those observed during total solar eclipses (TSEs) and with coronagraphs. This radiative-DEM (R-DEM) inversion utilizes visible and infrared emission lines that are excited by photospheric radiation out to at least 3R ⊙. Specifically, we use the Fex (637 nm), Fexi (789 nm), and Fexiv (530 nm) coronal emission lines observed during the 2019 July 2 TSE near solar minimum. We find that, despite a largeT e spread in the inner corona, the distribution converges to an almost isothermal yet bimodal distribution beyond 1.4R ⊙, withT e ranging from 1.1 to 1.4 in coronal holes and from 1.4 to 1.65 MK in quiescent streamers. Application of the R-DEM inversion to the Predictive Science Inc. magnetohydrodynamic simulation for the 2019 eclipse validates the R-DEM method and yields a similar LOSTe distribution to the eclipse data. -
Abstract On 2017 August 21, the Airborne Infrared Spectrometer (AIR-Spec) observed the total solar eclipse at an altitude of 14 km from aboard the NSF/NCAR Gulfstream V research aircraft. The instrument successfully observed the five coronal emission lines that it was designed to measure: Si
x 1.431μ m, Sxi 1.921μ m, Feix 2.853μ m, Mgviii 3.028μ m, and Siix 3.935μ m. Characterizing these magnetically sensitive emission lines is an important first step in designing future instruments to monitor the coronal magnetic field, which drives space weather events, as well as coronal heating, structure, and dynamics. The AIR-Spec instrument includes an image stabilization system, feed telescope, grating spectrometer, and slit-jaw imager. This paper details the instrument design, optical alignment method, image processing, and data calibration approach. The eclipse observations are described and the available data are summarized. -
Abstract This letter capitalizes on a unique set of total solar eclipse observations acquired between 2006 and 2020 in white light, Fe
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