A new method to predict solar flares more than a day before they occur has been found by researchers at Purdue University. This helps in providing advance warning to help protect satellites, power grids and astronauts from potentially dangerous radiation.
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 hypothesis 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 hypothesis, which is supported with 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 beginning 39 hours before a large solar flare.
Since then, researchers have been examining similar variation in decay rates before solar flares, as well as those resulting from Earth's orbit around the sun and changes in solar rotation and activity.
"It's the first time the same isotope has been used in two different experiments at two different labs, and it showed basically the same effect," Fischbach said.
Data were recorded during routine weekly calibration of an instrument used for radiological safety at Ohio State's research reactor. Findings showed a clear annual variation in the decay rate of a radioactive isotope called chlorine 36, with the highest rate in January and February and the lowest rate in July and August, over a period from July 2005 to June 2011.
The new observations support previous work by Jenkins and Fischbach to develop a method for predicting solar flares. Advance warning could allow satellite and power grid operators to take steps to minimize impact and astronauts to shield themselves from potentially lethal radiation emitted during solar storms.
The Purdue experimental setup consists of a radioactive source - manganese 54 - and a gamma-radiation detector. As the manganese 54 decays, it turns into chromium 54, emitting a gamma ray, which is recorded by the detector to measure the decay rate.
Purdue has filed a U.S. patent application for the concept.
The findings appeared online last week in the journal Astroparticle Physics.