Fig. 2

a (From the top) Three components (Bx, By, Bz) of the interplanetary magnetic field (IMF), velocity (Vsw) and ion density (Ion N) of the solar wind observed by ACE at the Lagrangian point-1 (L1) during the geomagnetic storm on 22 June, 2015. The time of the ACE data is shifted by 35 min so that we can see the correspondence between the sudden increases in the solar wind density and speed and the geomagnetic sudden commencement on the ground (SC). b SYM-H and ASY-H geomagnetic indices from WDC C2 Kyoto