During sporadic eruptions in the solar atmosphere, such as solar flares and coronal mass ejections (CMEs), very energetic solar particles are produced. These particles can reach Earth quickly, sometimes within a quarter of an hour, and can significantly alter radiation levels in the atmosphere and even at ground levels.
These intense events, known as ground level enhancements (GLEs), are potentially hazardous for aircraft electronics and passengers, particularly those flying over the poles, where there is less protection from Earth’s magnetic shield. In a new study, Mishev and Usoskin calculated the radiation levels passengers would be exposed to during a typical commercial flight over the pole, simulating the radiation levels present throughout a GLE.
When solar particles hit Earth’s atmosphere, they induce nucleonic-electromagnetic-muon showers and cause an increase in secondary particles bombarding the ground and detected by the Global Neutron Monitor Network, a system of ground-based monitoring stations around the world. When such an increase is recorded simultaneously by at least two monitors and a spaceborne probe, a GLE alert is set.
To determine how much radiation commercial airline passengers and crew are likely to be exposed to during a GLE, the team examined data from one such event, which occurred on 10 September 2017. During the week leading up to that date, several solar flares and CMEs were observed, and a flare with a CME on 10 September triggered a globally observed event called GLE 72, detected by the monitor network. Using the network’s data, the team modeled likely radiation exposure during two transcontinental polar flights at several cruise flight altitudes ranging from 30,000 to 50,000 feet (about 9 to 15 kilometers).
In the worst-case scenario, in which the airplanes took off close to the onset of the GLE and maintained a high cruise altitude of 40,000 feet (12 kilometers), passengers on a flight from Helsinki, Finland, to Osaka, Japan, would have received a roughly 90-microsievert dose of radiation, the team found. A flight from Helsinki to New York would have received a slightly higher dose, around 110 microsieverts.
Such levels are far below an average American’s annual radiation exposure of 1 millisievert. But they remain above typical background radiation and could pose a cumulative health risk for aircraft crew and pilots, who already receive roughly triple the average yearly dose of radiation. Radiation can also upset or damage the sensitive electronics aboard commercial aircraft, underscoring the importance of preparing for severe space weather. (Space Weather, https://doi.org/10.1029/2018SW001946, 2018)
—Emily Underwood, Freelance Writer