Solar proton event
From Glossary of Meteorology
solar proton event
(Abbreviated SPE.) Strong enhancement in energetic proton flux (typically >10 MeV), commonly from a shock caused by an energetic solar eruption. SPEs can be detected throughout the heliosphere; however, for space weather purposes, they are characterized by the episodic detection and measurement of proton flux reaching and sustaining 10 particle flux units (1 PFU = 1 particle per square cm per second per steradian) for at least 15 minutes at energies >10 MeV by the primary NOAA satellite or GOES. Periods of at least 10 PFU at the 10-MeV level are also referred to as solar proton events or radiation storms and are quantified by the use of the National Oceanic and Atmospheric Administration S-scale.
Space Weather Prediction Center, 2018: Solar radiation storm. Accessed 14 August 2018. Available at https://www.swpc.noaa.gov/phenomena/solar-radiation-storm.
Term edited 14 August 2018.