Coronal Densities, Temperatures and Abundances During the 2019 Total Solar Eclipse: The Role of Multi-Wavelength Observations in Coronal Plasma Characterization

Abstract

The Airborne Infrared Spectrometer (AIR-Spec) offers an unprecedented opportunity to explore the Near Infra-Red (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 (July 2, 2019) was shifted to cover two density sensitive lines from S XI. In this paper we study detailed diagnostics for temperature, electron density and elemental abundances by comparing results from AIR-Spec slit positions above the east and the west limb with those from Hinode/EIS, the PolarCam detector and SDO/AIA. We find very good agreement in the electron densities obtained from the EIS EUV line ratios, those from the NIR S XI ratio and those obtained from the polarized brightness PolarCam measurements. Electron densities ranged from Log Ne [cm${}^{-3}]$ = 8.4 near the limb, falling to 7.2 at $R_0=1.3$. EIS spectra indicate that the temperature distribution above the west limb is near-isothermal at around 1.3 MK, while that on the east has an additional higher-T component. The AIR-Spec radiances in Si X and S XI as well as the AIA data in the 171, 193, and 211 Angstroms bands are consistent with the EIS results. EIS and AIR-Spec data indicate that the sulphur abundance (relative to silicon) is photospheric in both regions, confirming our previous results of the 2017 eclipse. The AIA data also indicate that the absolute iron abundance is photospheric. Our analysis confirms the importance of the diagnostic potential of the NIR wavelength range, and that this important wavelength range can be used reliably and independently to determine coronal plasma parameters.

Accepted for publication

References in corpus (10)

• CHIANTI -- an atomic database for emission lines -- Paper XVI: Version 10, further extensions
• Global maps of the magnetic field in the solar corona
• Element Abundances: A New Diagnostic for the Solar Wind
• Solar coronal lines in the visible and infrared. A rough guide
• Identifying the Coronal Source Regions of Solar Wind Streams from Total Solar Eclipse Observations and in situ Measurements Extending Over a Solar Cycle
• The EUV spectrum of the Sun: quiet and active Sun irradiances and chemical composition
• The Solar Minimum Eclipse of 2019 July 2: II. The First Absolute Brightness Measurements and MHD Model Predictions of Fe X, XI and XIV out to 3.4 Rs
• New deep coronal spectra from the 2017 total solar eclipse
• Electron Densities in the Solar Corona Measured Simultaneously in the Extreme-Ultraviolet and Infra-Red
• Multi-wavelength observations by XSM, Hinode and SDO of an active region. Chemical abundances and temperatures

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• Assessing the capability of a model-based stellar XUV estimation
• Reduced atomic models for large-scale computations: Fe XIII near-infrared lines
• Extreme-ultraviolet (EUV) observables of simulated plasmoid-mediated reconnection in the solar corona