The system works by measuring differences in gamma radiation emitted when atoms in radioactive elements "decay," or lose energy. This rate of decay is widely believed to be constant, but recent findings challenge that long-accepted rule.

The new detection technique is based on a theory that radioactive decay rates are influenced by solar activity, possibly streams of subatomic particles called solar neutrinos. This influence can wax and wane due to seasonal changes in the Earth's distance from the sun and also during solar flares, according to the theory, which is supported by data published in a dozen research papers since it was proposed in 2006, said Ephraim Fischbach, a Purdue University professor of physics.

Fischbach and Jere Jenkins, a nuclear engineer and director of radiation laboratories in the School of Nuclear Engineering, are leading research to study the phenomenon and possibly develop a new warning system. Jenkins, monitoring a detector in his lab in 2006, discovered that the decay rate of a radioactive sample changed slightly 39 hours before a large solar flare.

Since then, researchers at Purdue have seen similar variation in decay rates before solar flares. The phenomenon represents a possible way to predict solar flares, allowing satellite and power grid operators to take steps to minimize impact and astronauts to take cover from potentially lethal charged particles emitted during solar storms, Fischbach said.

Large solar flares may produce a "coronal mass ejection" of highly energetic particles, which can interact with the Earth's magnetosphere, triggering geomagnetic storms that sometimes knock out power. Solar activity is expected to peak over the next year or so as part of an 11-year cycle that could bring strong solar storms, he said.