Danger zones in the air where radiation levels surge could pose an unrecognised health hazard. Airliners may have to avoid these in future, just as they do with volcanic ash clouds, to minimise any risk to travellers and crew.
We have long known that high-altitude flight exposes us to cosmic rays. The radiation dose on a flight from London to Tokyo is roughly equivalent to a chest X-ray.
Now research flights have revealed the existence of “clouds” where radiation levels can be at least double the usual level. They were discovered as a result of the NASA-funded Automated Radiation Measurements for Aerospace Safety (ARMAS) programme, which aims to develop new methods of measuring and monitoring high-altitude radiation.
In 265 flights, radiation levels detected generally followed the expected pattern, but in at least six instances they surged, as though the aircraft was flying through a radiation cloud.
“We have seen several cases where the exposure is doubled while flying through the cloud,” says ARMAS principal investigator W. Kent Tobiska, of Los Angeles firm Space Environment Technologies. “It is quite variable and can easily be more or less than that.”
Even higher levels have been recorded in some cases, but those results remain unpublished while the team considers alternative explanations for the data.
Tobiska says the two main sources of radiation, cosmic rays and the solar wind, can’t account for the surges. “Our new measurements show a third component.”
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