Observation of CHASE at 08:26:33 UT. The dashed cyan line represents the path along the spine of the filament, and a red point P is on it. Spectrum profiles of point P at different times are shown in panel (b), and the black line represents the line profile of the quiet region. Panel (c) shows the spectrum-time diagram of point P. Panel (d) shows the spectrum along the path at 08:20:36 UT. The vertical black line represents the position of point P.