Figure 4. Statistical results of the global distribution of reversed proton energy spectrum during 2013-2016 under the indicated three geomagnetic conditions (from left to right: Dst > -30 nT, -50 nT < Dst < -30 nT, and Dst < -50 nT). (a-c) samples, (d-f) occurrence rate, (g-i) the proton energy of flux maximum, (j-l) the proton energy of flux minimum, and (m-o) the ratio of the proton flux maximum to minimum.