RADS ON A PLANE--THE RETURN FLIGHT

RADS ON A PLANE--THE RETURN FLIGHT

Regular readers of Spaceweather.com have been following the travels of Tony Phillips, who spent the past week flying commercial jets back and forth across the USA for meetings in Washington DC. In addition to his usual baggage, he carried a pair of radiation sensors onboard. Sitting in the economy section of a US Airways flight from Reno to Phoenix on Nov. 11th, Phillips recorded dose rates which were almost 30 times higher than background dose rates at ground level. On Nov. 15th, he gathered data from a return leg, American Airlines flight 2407 from Washington DC to Chicago. It was only half as bad:

The radiation inside these planes comes from space--that is, cosmic rays that penetrate Earth's atmosphere and reach down to aviation altitudes. In the plot we can see what a difference altitude makes: Cruising at 39,000 feet, the Reno to Phoenix flight was closer to space and thus experienced double the radiation of the DC to Chicago flight cruising at 28,000 feet.
The radiation sensor Phillips used to make these measurements is the same one that Earth to Sky Calculus routinely flies onboard helium balloons to measure cosmic rays in the stratosphere. It detects X-rays and gamma-rays in the energy range 10 keV to 20 MeV, similar to energies used by medical X-ray machines and airport security scanners.
We can put these doses into context by comparing them to medical X-rays. In a single hour flying between Reno and Phoenix on Nov. 11th, the passengers were exposed to about the same amount of radiation as an X-ray at the dentist's office. Such a dose is not a big deal for an occasional flier, but as NASA points out, frequent fliers of 100,000 miles or more can accumulate doses equal to 20 chest X-rays or about 100 dental X-rays. Lead aprons, anyone?
Some experts reading these reports on Spaceweather.com have pointed out that X-rays and gamma-rays represent only a fraction of the radiation present at aviation altitudes. The true dose could be doubled or tripled by neutrons, a component of cosmic rays known to be especially good at delivering energy to human tissue.

From SpaceWeather.com