Fig. 40.

Left Arrival of ${}^4$He ions of different energies at the Wind s/c during the May 6, 1998 GLE. Right Ion intensity onset time in each energy interval versus 1/v. Parameters of the linear fit (solid line) are: slope gives the path-length, and the intercept yields the SPR time at the Sun. Image reproduced with permission from Reames (2009b), copyright by AAS