Probability density functions for the non-thermal velocity and Doppler velocity relation for the upflow region (top panels) and the active region core (bottom panels) for the observation from 15 November 2017. For the upflow region panels (top row), the number in the right corner shows the linear correlation coefficient. For the active region core panels (bottom row), the number in the right corner represents a non-linear Spearman’s rank correlation. The panel of the Si IV line in the active region core shows a dichotomy. Thus, we additionally calculated the non-linear correlation coefficient separately for the negative, positive, and absolute Doppler velocity and obtained −0.39, 0.74, and 0.62, respectively.