HMI continuum light curves showing very weak WL emissions during the flare at four different positions. (a1) and (a2): HMI continuum map and LOS magnetogram of the NOAA 12673 at the time of 09:09:45 UT on September 6, 2017. The four ‘×’ symbols in different colours mark the positions where we show the HMI continuum light curves. (b1)–(b4): Corresponding HMI continuum light curves at four different positions. The vertical purple lines mark the beginning and end times of the 1600 Å impulsive emission at the position. The corresponding WL enhancements ((I_p − I₀)/I₀) are given at the top of these panels.