  We present high-resolution and multi-line observations of a C2-class solar
flare, occurred in NOAA AR 12740 on May 6, 2019. The rise, peak and decay
phases of the flare were recorded continuously and quasi-simultaneously in the
Ca II K line with the CHROMIS instrument, the Ca II 8542 and Fe I 6173 \AA
lines with the CRISP instrument at the SST. The observations in the
chromospheric Ca II lines exhibit intense brightening near the flare
footpoints. At these locations, a non-LTE inversion code was employed to infer
the temperature, magnetic field, line-of-sight (LOS) velocity and
microturbulent velocity stratification in the flaring atmosphere. During the
flare peak time, the LOS velocity shows both upflows and downflows around the
flare footpoints in the upper chromosphere and lower chromosphere,
respectively. Moreover, the temporal analysis of the LOS magnetic field at the
flarepoints exhibits a maximum change of ~600 G. After the flare, the LOS
magnetic field decreases to the non-flaring value, exhibiting no permanent or
step-wise change. The analysis of response functions to the temperature, LOS
magnetic field and velocity shows that the Ca II lines exhibit enhanced
sensitivity to the deeper layers (i.e., log_t ~ -3) of the flaring atmosphere,
whereas for the non-flaring atmosphere they are mainly sensitive around log_t ~
-4. We suggest that a fraction of the apparent increase in the LOS magnetic
field at the flare footpoints may be due to the increase in the sensitivity of
the Ca II 8542 \AA line in the deeper layers, where the field strength is
relatively stronger. The rest can be due to magnetic field reconfiguration
during the flare. Our observations illustrate that even a less intense C-class
flare can heat the deeper layers of the solar chromosphere, mainly at the flare
footpoints, without affecting the photosphere.
