Fig. 1
From: History and development of coronal mass ejections as a key player in solar terrestrial relationship
a The 1909 May 12 solar eruption photographed by G. E. Hale in H-alpha. A filament erupted from a sunspot group located at S13E15, which was a good location for an eruption to have direct impact on Earth (from Hale 1931). In modern terminology, this is a two-ribbon flare, typically formed after a filament eruption. Flares from locations like this were followed by geomagnetic storms. b The open circles correspond to small storms, while the filled circles correspond to great storms. Encircled, filled symbols denote the outstanding storms that occurred over an 85-year period starting in 1859 (from Newton 1943)