Time profiles for three GLEs, on 2001 Apr 15 (left), 1989 Nov 15 (middle) and 1982 Dec 7 (right). The ordinate displays the fractional count rate excess above the galactic cosmic ray level. The observed profile is in black; the two-exponential profile fitted to the observation is shown by the red continuous line, and the scaled median profile of GLEs established in Section 3 is shown by the dashed blue line.