Natural disaster
A solar flare is a phenomenon where the Sun suddenly releases a great amount of solar radiation, much more than normal. Solar flares are unlikely to cause any direct injury, but can destroy electrical equipment. The potential of solar storms to cause disaster was seen during the 1859 Carrington event, which disrupted the telegraph network, and the March 1989 geomagnetic storm which blacked out Quebec. Some major known solar flares include the X20 event on August 16, 1989, and a similar flare on April 2, 2001. The most powerful flare ever recorded occurred on November 4, 2003 (estimated at between X40 and X45).
Neutron monitor
Approximately 10-15 times per decade, the Sun emits particles of sufficient energy and intensity to raise radiation levels on Earth's surface. The official list of GLEs is kept by the International GLE database. The largest of these events, termed a "ground level enhancement" (GLE) was observed on February 23, 1956. The most recent GLE, (#72) occurred on September 10, 2017 as a result of an X-class flare and was measured on the surface of both the Earth (by Neutron Monitors) and Mars (by the Radiation Assessment Detector on the Mars Science Laboratory's Curiosity Rover).