Spectroscopic Inversions of the Ca ii 8542 Line in a C-class Solar Flare

• Published in: The Astrophysical journal 2017-09, Vol.846 (1), p.9
• Main Authors: Kuridze, D., Henriques, V., Mathioudakis, M., Koza, J., Zaqarashvili, T. V., Rybák, J., Hanslmeier, A., Keenan, F. P.
• Format: Article
• Language: English
• Subjects: Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHROMOSPHERE; COMPARATIVE EVALUATIONS; HEATING; Image resolution; Inversions; Lower atmosphere; LTE; Optical analysis; Optical thickness; PHOTOSPHERE; RADIANT HEAT TRANSFER; radiative transfer; SOLAR FLARES; SPECTROSCOPY; STRATIFICATION; SUN; Sun: atmosphere; Sun: chromosphere; Sun: flares; Sun: photosphere; techniques: imaging spectroscopy; TELESCOPES; Temperature; VELOCITY; Velocity distribution
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/aa83b9

We study the C8.4-class solar flare SOL2016-05-14T11:34 UT using high-resolution spectral imaging in the Ca ii 8542 line obtained with the CRISP imaging spectropolarimeter on the Swedish 1 m Solar Telescope. Spectroscopic inversions of the Ca ii 8542 line using the non-LTE code NICOLE are used to investigate the evolution of the temperature and velocity structure in the flaring chromosphere. A comparison of the temperature stratification in flaring and non-flaring areas reveals strong footpoint heating during the flare peak in the lower atmosphere. The temperature of the flaring footpoints between log τ 500 − 2.5 and − 3.5 , where τ500 is the continuum optical depth at 500 nm, is ∼ 5 - 6.5 kK close to the flare peak, reducing gradually to ∼ 5 kK . The temperature in the middle and upper chromosphere, between log τ 500 − 3.5 and −5.5, is estimated to be ∼6.5-20 kK, decreasing to preflare temperatures, ∼5-10 kK, after approximately 15 minutes. However, the temperature stratification of the non-flaring areas is unchanged. The inverted velocity fields show that the flaring chromosphere is dominated by weak downflowing condensations at the formation height of Ca ii 8542 .