Normally, solar radiation storms are held at bay by our planet's magnetic field and upper atmosphere. On Sept.10th, however, there was a "ground level event" (GLE). Neutron monitors in the Arctic, Antarctic, and several other high latitude locations detected a surge of particles reaching all the way down to Earth's surface:
However, that does not mean the Sept.10th GLE was negligible. Dyer says that "passengers flying on high-latitude routes at 40,000 feet could have absorbed an extra 10 microSieverts of radiation. During the first hour of the GLE, the dose rate inside the aircraft during such a flight would have approximately doubled."
He also notes that the GLE could have caused minor upsets of onboard electronics and avionics, although nothing on the scale of the epic 1956 GLE, "which would be very challenging to modern systems."
"Since measurements began around 1942 there have now been 73 events detected by ground level radiation monitors," Dyer adds. "The Sept.10, 2017, event is far from the strongest, but it is of special interest because it demonstrates the need for continual vigilance even during Solar Minimum." www.spaceweather.com