A major solar particle storm was registered by neutron monitors of SGO

​In mid-September 2017 the Sun shot a series of very strong flares. Those eruptive events lead, in particular, to acceleration of charged protons up to very high energies forming a strong solar particle storm. These energetic solar particles are known as solar cosmic rays, and they are important for science as bringing information on acceleration mechanisms at the Sun and provide a probe of the interplanetary medium. They are not only of an academic interest since they form an important technological hazard and are dangerous for satellites and for astronauts and event crew/passengers of transpolar commercial jets, thus a continuous monitoring of such events is provided, in particular by dedicated instruments operated by Sodankylä Geophysical Observatory of the University of Oulu.

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.

This particle storm has been registered by several neutron monitors around the world, including ones in Linnanmaa, Oulu and the Concordia station in Antarctica, both belonging to the University of Oulu (Sodankylä Geophysical Observatory). The Antarctic neutron monitor yielded the highest among all the stations of the worldwide network, thanks to its unique location.

Now the event is under detailed analysis by several independent scientific groups including the cosmic ray group of the University of Oulu.