August 14, 2012
New Research Could Help Predict Solar Storms
Lee Rannals for redOrbit.com - Your Universe Online
Predicting solar flares still remains a hit-or-miss task for scientists, but new research may shed more light on helping to predict just when the events could occur.
The prediction system works by measuring differences in gamma radiation emitted when atoms in radioactive elements "decay," or lose energy. This decay rate is believed to be constant, but recent findings challenge that theory.
The new technique is based on a hypothesis that radioactive decay rates are influenced by solar activity. This influence can wax and wane due to seasonal changes in the Earth's distance from the sun and also during solar flares.
The researchers have been examining similar variations 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," Ephraim Fischbach, a Purdue University professor of physics, said in a prepared statement.
The team used data recorded during routine weekly calibrations of an instrument used for radiological safety at Ohio State's research reactor.
During the calibration, findings showed a clear annual variation in the decay rate of a radioactive isotope called chlorine 36, showing the highest rate in January and February, and the lowest in July and August.
The observations support previous work by the team to develop a method for predicting solar flares. The findings agree with data previously collected at the Brookhaven National Laboratory regarding the decay rate of chlorine 36.
Fischbach said changes in the decay rate were found to match changes in the Earth-sun distance and Earth's exposure to different parts of the sun itself.
Large solar flares may produce a coronal mass ejection (CME) of highly energetic particles, which ultimately help create solar storms.
Satellites could be designed to shut down temporarily to keep safe from massive solar storms, and power grids could also be safeguarded in a similar way before the storm arrives.
"We have repeatedly seen a precursor signal preceding a solar flare," Fischbach said. "We think this has predictive value."
The team's set up consists of a radioactive source and a gamma-ray detector. As the radioactive source, manganese 54, decays, it turns into chromium 54, emitting a gamma ray. This is recorded by the detector to measure the decay rate.
Research findings show the phenomenon is influenced by the Earth's distance from the sun.
"When the Earth is farther away, we have fewer solar neutrinos and the decay rate is a little slower," said Jere Jenkins, a nuclear engineer and director of radiation laboratories in the School of Nuclear Engineering. "When we are closer, there are more neutrinos, and the decay a little faster."
The team also was able to record both increases and decreases in decay rates during solar storms.
"What this is telling us is that the sun does influence radioactive decay," Fischbach said.
He said neutrinos have the least mass of any known subatomic particle, but it is plausible that they somehow affect the decay rate.
"Since neutrinos have essentially no mass or charge, the idea that they could be interacting with anything is foreign to physics," Jenkins said. "So, we are saying something that doesn't interact with anything is changing something that can't be changed. Either neutrinos are affecting decay rate or perhaps an unknown particle is."
He discovered the effect by chance in 2006, when he was watching television coverage of astronauts spacewalking. While watching, a solar flare had erupted and was posing a threat to those on board the International Space Station. He checked his equipment, and discovered that a change in decay-rate had preceded the solar flare.
He said further research is needed to confirm the findings, and to expand the work by using more sensitive equipment.
Their findings were published last week in the journal Astroparticle Physics.