Figure 1. An overview of the 17 March 2015 strong geomagnetic storm. (a) solar wind speed (Vsw) and interplanetary magnetic field (IMF) Bz, (b) Dst and AE indices, (c-e) 90° pitch angle proton fluxes at energies of ~44.7 keV, ~81.6 keV, and ~268.9 keV, respectively, with the black solid lines indicating the plasmapause location. (f-h) The proton energy spectra at L ~ 2.8 - 5.6 during three indicated time intervals of the storm.