At 15:35UT, 10 September 2017 a strong solar flare of class X8.2 and a consecutive ejection of solar matter caused acceleration of particles, which hit Earth at 16:15UT. The storm was so strong, that the high-energy fraction of solar particles passed through the atmosphere and reached the ground. Such events are quite rare: two previous ones took place in May 2012 and December 2006.
|Concordia research station in Antarctica; photo ESA/IPEV/ENEAA/A.Kumar and E. Bondoux.|
Now the event is under detailed analysis by several independent scientific groups including the cosmic ray group of the University of Oulu.