Spectral profiles of HMI Fe I 6173 Å at four different positions. (a) and (b): HMI continuum intensity map and LOS magnetogram, respectively. The orange ‘×’ marks the four positions. (e) and (f): HMI Fe I 6173 Å spectral profiles for the four positions at three different times, i.e. 08:48 UT (yellow), 09:00 UT (blue), and 09:12 UT (purple). 08:48 UT and 09:00 UT are before the flare, while 09:12 UT is around the peak of flare. All the spectral profiles are normalized (I_i/I_q, i = 0, 1, 2, 3, 4, 5) by the average continuum intensity (I_q) in the quiet region marked by the dashed brown box in panel a.