New Observations of the IR Emission Corona from the July 2, 2019 Eclipse Flight of the Airborne Infrared Spectrometer

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Jenna E. Samra, Peter Cheimets, Edward E. DeLuca, Chad A. Madsen, Vanessa Marquez, Naylynn Tañón Reyes

The Airborne Infrared Spectrometer (AIR-Spec) was commissioned during the 2017 total solar eclipse, when it observed five infrared coronal emission lines from the Gulfstream V High-performance Instrumented Airborne Platform for Environmental Research (GV HIAPER), a research jet owned by the National Science Foundation (NSF) and operated by the National Center for Atmospheric Research (NCAR). The second AIR-Spec research flight took place during the July 2, 2019 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 XI 1.393 μm, Si X 1.431 μm, S XI 1.921 μm, and Fe IX 2.853 μm. The 1.393 μm line, half of a density-sensitive S XI line pair, was detected for the first time. The 2017 AIR-Spec detection of Fe IX was confirmed and the first observations were made of the Fe IX intensity as a function of solar radius. Observations of S XI and Si X were used to estimate the temperature and density above the east and west limbs, the subject of a future paper. Atmospheric absorption was significant in the 2019 data, and atmospheric modeling was required to extract accurate line intensities. 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 flight. The thermal background was reduced by a factor of 30, providing a 5.5x improvement in signal-to-noise ratio, and the pointing stability was improved by a factor of five to <10 arcsec RMS after image co-alignment. In addition, two imaging artifacts were identified and resolved, making the 2019 data easier to interpret and improving the spectral resolution by up to 50%.

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