Comparison of HXI flux and CHASE Doppler velocity. Panel (a) shows an AIA 94 Å map during the solar flare, with HXR 13−18 keV emissions at 90%, 70%, and 50% levels indicated by red contours. Panel (b) shows the HXI 13−18 keV flux (red) and CHASE Hα Doppler velocity (black) for the region of the HXR 13−18 keV emission source (red rectangle in panel e), with gray dotted lines marking their peak times. Panels (c)–(d) are similar to panels a–b, but corresponding to the HXR 19−30 keV flux (blue) and Doppler velocity (black) of its source (blue rectangle in panel e). Panel (e) shows the CHASE Hα line-core image at 14:43:33 UT, with the Doppler velocity calculation areas from panels b and d indicated by the red and blue boxes, respectively. Panel (f) shows the scatterplots of Doppler velocities versus the HXR 13−18 keV (red) and 19−30 keV (blue) fluxes, with the Pearson correlation coefficients labeled.