Radiation over Atlantic (reprise) October 19, 2008Posted by dorigo in personal, physics, science, travel.
Tags: cosmic rays, radiation
Earlier this month I pasted here a graph showing the level of radiation over the Atlantic ocean, recorded by a digital dosimeter I carried with me. I like that device: it is fun to see it becoming alive and counting real cosmic radiation as the plane climbs up the atmosphere (at sea level the thorium contamination inside buildings is the largest source of counts).
On that occasion, I found a strange effect toward the end of my trip over the Atlantic ocean, flying westward. It looked as if there were two dips in the intensity, which I was unable to explain (a list of possible effects was given in the other post). I did the same experiment on my flight back yesterday, with a halved integration time (half-hour intervals instead than one-hour intervals), as suggested by a reader. The results are shown in the graph below, which is collected flying eastward this time:
As you can see, there is a clear dip in the integrated dose (the blue curve) two and a half hours into the flight. Other features of the graph are the remarkable smoothness of both the integrated dose and the maximum recorded flux (the purple line). I am even a bit surprised by the smallness of the fluctuations of the latter: the maximum flux is basically a record of the highest deposited energy, the tail of the distribution of recorded rates. It all goes in the direction of confirming that the measurements are trustworthy.
The location of the dip approximately coincides with the region where the former graph showed one of its two dips, so the new data somehow agrees with the hypothesis that those dips are real variations in the cosmic-ray flux, maybe due to disuniformities in the magnetic field and/or solar wind effects. In other words, while the new data cannot really tell which is the source of the dips, I think they strengthen the hypothesis that the dips are not instrumental artifacts. The instrument in question is, I believe, one of the best devices available in commerce to record personal radiation exposure, and I would indeed be surprised if it failed so clearly.