Spectroscopic inversions of the Ca ii 8542 {\AA} line in a C-class solar flare

We study the C8.4 class solar flare SOL2016-05-14T11:34 UT using high-resolution spectral imaging in the Ca ii 8542 {\AA} line obtained with the CRISP imaging spectropolarimeter on the Swedish 1-m Solar Telescope. Spectroscopic inversions of the Ca ii 8542 {\AA} line using the non-LTE code NICOLE are used to investigate the evolution of the temperature and velocity structure in the flare 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 continuum optical depth at 500~nm, $\mathrm{l}\mathrm{o}\mathrm{g}{\tau }_{500}\approx -2.5\mathrm{a}\mathrm{n}\mathrm{d}-3.5$ is $\sim 5-6.5\mathrm{k}\mathrm{K}$, close to the flare peak, reducing gradually to $\sim 5\mathrm{k}\mathrm{K}$. The temperature in the middle and upper chromosphere, between $\mathrm{l}\mathrm{o}\mathrm{g}{\tau }_{500}\approx -3.5\mathrm{a}\mathrm{n}\mathrm{d}-5.5$, is estimated to be $\sim 6.5-20\mathrm{k}\mathrm{K}$, decreasing to pre-flare temperatures, $\sim 5-10\mathrm{k}\mathrm{K}$, 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 Ca ii 8542 {\AA} formation height.