Chromospheric light curve in the vicinity of the photospheric blueshifts. The solid black line represents a 3-point smoothing to the observed relative intensity (black filled circles). The relative intensity is the excess over the time-averaged background intensity. The grey horizontal bars represent the moments of the BSF’s existence. The blue filled circles and solid line correspond to the mean LOS velocity in the BSF estimated from HMI dopplergrams, whose scaling is indicated on the right y-axis. The black and blue arrows at the bottom half of the plot indicate local maxima in the chromospheric light curve and photospheric LOS velocities, respectively.