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The Strange Case of Solar Flares and Radioactive Decay Rates
DarkKnightRadick writes "Current models for radioactive decay have been challenged by, of all sources, the sun. According to the article, 'On Dec 13, 2006, the sun itself provided a crucial clue, when a solar flare sent a stream of particles and radiation toward Earth. Purdue nuclear engineer Jere Jenkins, while measuring the decay rate of manganese-54, a short-lived isotope used in medical diagnostics, noticed that the rate dropped slightly during the flare, a decrease that started about a day and a half before the flare.' This is important because the rate of decay is very important not just for antique dating, but also for cancer treatment, time keeping, and the generation of random numbers. This isn't a one time measurement, either. 'Checking data collected at Brookhaven National Laboratory on Long Island and the Federal Physical and Technical Institute in Germany, they came across something even more surprising: long-term observation of the decay rate of silicon-32 and radium-226 seemed to show a small seasonal variation. The decay rate was ever so slightly faster in winter than in summer.'"
One way to double-check the seasonal variation effect is to look at the output level on radioisotope power sources in spacecraft. Cooper (2008) found no relationship between radioactive decay and distance to the sun.
They found the same results in historical data of various labs. That of course does not rule out such a mundane reason, it makes it less likely.
I agree that there are certainly seasonal variations in labs, even if you try to keep it as constant as possible. But for starters the air in the lab has to be refreshed all the time, and this air comes from the outside. I can imagine the composition changes between summer and winter (plants don't grow in winter).
The 33-day cycle another replier mentioned is interesting of course, as it correlates with a solar cycle and no normal human cycles.
A multi-year cycle correlating to solar spots could be interesting.
Effects correlating to known solar flares too.