jeudi 17 mai 2018, par Jenna Samra (Harvard-Smithsonian Center for Astrophysics, USA)
Lundi 9 juillet 2018 à 11h00 , Lieu : Salle de confĂ©rence du bâtiment 17
On August 21, 2017, the Airborne Infrared Spectrometer (AIR-Spec) observed the total solar eclipse at an altitude of 14.3 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 (1.43µm), S XI (1.92µm), Fe IX (2.84µm), Mg VIII (3.03µm), and Si IX (3.94µm). Characterizing these magnetically sensitive emission lines is an important first step in designing future instruments to monitor the coronal magnetic field.
During the eclipse observation, AIR-Spec measured the average linewidths, peak intensities, and center wavelengths of all five lines radially outward from the limb at four positions in the corona. One of the positions sampled a prominence, where a number of H I lines were also observed. The observation of Fe IX at 2.84µm was the first of that line. The radial intensity gradient of Si X was measured with high sensitivity, providing information on the dominant excitation processes for that line. The relative Doppler velocity of Si X was measured with a resolution of 5 km/sec, revealing variations across different coronal structures and an interesting case of bimodal velocities near the solar prominence.
AIR-Spec is a slit spectrometer that measures light over a 1.55 Rsun field of view in four spectral passbands between 1.4 and 4 µm. The package includes an image stabilization system, feed telescope, grating spectrometer, and slit-jaw imager. Several follow-on experiments are being proposed to expand on the results from the 2017 eclipse, including a re-flight of AIR-Spec during the 2019 total eclipse, development of a new spectrometer or spectropolarimeter to observe the 2020 eclipse, and a laboratory study of infrared coronal emission lines.
