Are airline passengers at risk from radiation in the form of galactic cosmic rays and occasional solar flares? Yes, says a new study published in Scientific Reports, but it advises against the aviation industry taking any drastic action.
Amid a steady stream of galactic cosmic rays and solar energetic particles raining down on planes, the higher altitude and latitude of flights, the higher radiation doses for crew and passengers.
That brings into play space tourism as well as aviation.
Since a large solar flare can cause double the annual exposure limit, action needs to be taken. The remedy is for planes to lower their altitude or change or cancel flight paths altogether.
That significantly raises expenses for airlines. Is it worth it? No, says the new research from Kyoto University, Japan, which indicates that the frequency of major solar flares that would cause a problem is only about once every 17 years.
What are galactic cosmic rays?
Galactic cosmic rays (GCR) are always bombarding Earth’s atmosphere. Originating from the gas and dust between the stars, this energetic background source of charged particles varies as it interacts with the Sun’s magnetic field, but not much.
The fluxes in GCR is stable and predictable, states the paper, with dose rates are no higher than 10 µSv/h—a safe level—at the normal cruising altitude of 40,000 ft. (7.5 miles/12 km).
What are solar flares?
Solar energetic particles (SEP) are another constant source of radiation. A stream of high-energy particles that comes our way every day and night from the Sun, Earth’s magnetic field mostly protects us—and displays beautiful aurora around the Arctic and Antarctic circles. But what about during big solar flares and coronal mass ejections (CMEs) that are unpredictable, but do happen?
We know that massive once-a-century solar storms could damage the electrical grid, communication systems and satellites—and most certainly the Internet—but what about aviation?
“During a large solar particle event we see sudden SEP fluxes with dose rates exceeding 2 mSv/h, but these are rare and short-lived,” said Kyoto University’s Yosuke Yamashiki, who led the research team.
That’s twice the annual exposure limit.
What is a ‘ground-level enhancement?’
A GLE is a unpredicted spike in radiation. In order to assess whether planes should mitigate the effects of these events, the research team assessed eight flight routes during five GLEs.
They estimate that the maximum flight route dose and dose rate arising from major GLE events would need to exceed 1 mSv and 80 µSv/h, respectively, before it was worth airlines taking action to protect passengers and staff.
In Japan, the Radiation Council sets a target value for radiation dose at 5 mSv per year for airline crew members, but only 1 mSv for passengers.
However, GLE events of a magnitude that could deliver passengers such a dose happen only once every 17 years for a maximum dose.
So does the risk justify the cost?
Since the cost of rerouting or delaying a flight could cost about $1,500 for a long-haul flight operating every day, probably not. “There is no denying the potentially debilitating effects of radiation exposure, but the data suggest that current measures may be over-compensating for the actual risks,” said Yamashiki.
What about space tourism?
Since the likes of Virgin Galactic and Blue Origin have now begun their space tourism endeavours, the threat from radiation ought to be quantified even more, argue the researchers. “Because the risk of solar radiation exposure is expected to be higher in the space travel plans of Space X, Virgin Galactic, and Blue Origin, it will be even more important to quantify the risk using the method developed in this study, to propose measures to reduce the exposure, and to develop risk mitigation plan,” reads the report. “However, in order to make concrete proposals, a more accurate risk assessment based on detailed operation plans is essential, and we will continue to conduct such research in cooperation with related organizations.”
Wishing you clear skies and wide eyes.