All-sky images (ASIs) at Athabasca, Canada, during SSS 3 on 11 May 2024. (a) ASI montages at every minute from 08:40 to 08:59 UT, directions are shown by arrows, UTs are mentioned for each of the ASIs; (b) ASI S-N keograms, Athabasca MLT is shown in the x-axis; and (c) SML variation. The substorm onset determined by the sharp SML decrease is marked by a vertical red short-dashed line, and the corresponding ASI is marked by a red downward arrow.