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Long lines. Narrow seats. Baggage fees. You recognize this list. It's the downside of flying on modern commercial airlines. And now we have a new item to add: neutrons.
Spaceweather.com and Earth to Sky Calculus have just completed a 5-continent survey of cosmic ray neutrons at aviation altitudes. From Dec. 2018 through Feb. 2019, Hervey Allen of the University of Oregon's Network Startup Resource Center carried Earth to Sky radiation sensors including neutron bubble chambers onboard commercial flights from North America to Europe, Africa, South America and Asia. Neutrons from deep space were detected on every flight.
Hervey logged 83 hours in the air as he traveled 41,500 miles above 30,000 feet. For reference, that's almost twice the circumference of the Earth. The entire time, he gathered data on X-rays, gamma-rays and neutrons in an energy range (10 keV to 20 MeV) similar to that of medical radiology devices and "killer electrons" from the Van Allen Radiation Belts.
The results were eye-opening. During the trip, Hervey recorded 230 uGy (microGrays) of cosmic radiation. That's about the same as 23 panoramic dental x-rays or two and a half chest X-rays. Moreover, 41% of the dose came in the form of neutrons. This confirms that cosmic-ray neutrons are abundant at aviation altitudes and must be considered in any discussion of "Rads on a Plane."
https://spaceweatherarchive.com/2019/03/12/neutrons-detected-on-commercial-airplane-flights/
(Score: 2) by HiThere on Friday March 15 2019, @04:59PM (2 children)
I think you left out black body radiation. As the temperature of the earth increases, the amount of heat it radiates increases. IIRC this is a fourth power law. So it should mean you are overestimating the rise in temperature. (By how much, though?)
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(Score: 2) by Immerman on Friday March 15 2019, @05:21PM (1 child)
Not really - that's doesn't factor into things as much until you start looking at the *consequences* of the increased greenhouse gasses. If you increase the planet's temperature by 1*C, you increase the water in the atmosphere by somewhere around 7% to maintain equilibrium humidity.
Now, the consequences of increasing the amount of greenhouse gasses by 7% get more complicated - they make the atmosphere less transparent to IR (the frequency at which something the Earth's temperature radiates most black-body radiation), which means that the Earth must get warmer in order to radiate enough energy to restore equilibrium with the incoming solar radiation (very little of which is IR, because the sun is hot enough to radiate primarily in the visible spectrum)
Figuring out how much additional warming must occur to reach that new thermal equilibrium is where the black black-body formula comes into play, and means (along with other non-linearities) that the 7% increase in greenhouse gasses won't cause a full 7% increase in greenhouse warming (currently estimated at around 36C total, based on the discrepancy between measured and theoretical temperatures of something with the Earth's albedo). A simple linear extrapolation would expect that 7% increase in water to cause a about 2.5C of further warming.
However, there's also the fact that that increased warming will put even *more* water into the air to maintain stable humidity. Even if the actual temperature change associated with that 7% increase is only half the linear prediction, 1.25C, that still means you're going to further increase the amount of water in the air by another ~9% to maintain the same humidity. (and of course, that 9% will cause even more warming, which will cause even more evaporation...)
Meanwhile, at Earth's average temperature of about 288K, a 1C increase will only increase the black-body radiation by about (289/288)^4 -1 = 1.4%. If a 7% increase in greenhouse gas mapped directly to a 7% decrease in the transparency of the atmosphere to IR, you would need to increase the temperature to around 293K, a 5C difference, in order to restore energy equilibrium.
(Score: 2) by HiThere on Friday March 15 2019, @07:47PM
Thank you. I couldn't have even estimated that.
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