Stanford Report, August 23, 2010 
The strange case of solar flares and radioactive elements
When researchers found an unusual linkage between solar flares and  the inner 
life of radioactive elements on Earth, it touched off a  scientific detective 
investigation that could end up protecting the  lives of space-walking 
astronauts and maybe rewriting some of the  assumptions of physics.


BY DAN STOBER
It's a mystery that presented itself unexpectedly: The radioactive  decay of 
some elements sitting quietly in laboratories on Earth seemed  to be influenced 
by activities inside the sun, 93 million miles away.
Is this possible?

Researchers from Stanford and Purdue University believe it is. But  their 
explanation of how it happens opens the door to yet another  mystery.
There is even an outside chance that this unexpected effect is  brought about 
by 
a previously unknown particle emitted by the sun. "That  would be truly 
remarkable," said Peter Sturrock, Stanford professor  emeritus of applied 
physics and an expert on the inner workings of the  sun.
The story begins, in a sense, in classrooms around the world, where  students 
are taught that the rate of decay of a specific radioactive  material is a 
constant. This concept is relied upon, for example, when  anthropologists use 
carbon-14 to date ancient artifacts and when doctors  determine the proper dose 
of radioactivity to treat a cancer patient.

Random numbers
But that assumption was challenged in an unexpected way by a group of  
researchers from Purdue University who at the time were more interested  in 
random numbers than nuclear decay. (Scientists use long strings of  random 
numbers for a variety of calculations, but they are difficult to  produce, 
since 
the process used to produce the numbers has an influence  on the outcome.)

Ephraim Fischbach, a physics professor at Purdue, was looking into  the rate of 
radioactive decay of several isotopes as a possible source  of random numbers 
generated without any human input. (A lump of  radioactive cesium-137, for 
example, may decay at a steady rate overall,  but individual atoms within the 
lump will decay in an unpredictable,  random pattern. Thus the timing of the 
random ticks of a Geiger counter  placed near the cesium might be used to 
generate random numbers.)

As the researchers pored through published data on specific isotopes,  they 
found disagreement in the measured decay rates – odd for supposed  physical 
constants.

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.

Was this fluctuation real, or was it merely a glitch in the equipment  used to 
measure the decay, induced by the change of seasons, with the  accompanying 
changes in temperature and humidity?
"Everyone thought it must be due to experimental mistakes, because  we're all 
brought up to believe that decay rates are constant," Sturrock  said.

The sun speaks
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.

If this apparent relationship between flares and decay rates proves  true, it 
could lead to a method of predicting solar flares prior to  their occurrence, 
which could help prevent damage to satellites and  electric grids, as well as 
save the lives of astronauts in space.

The decay-rate aberrations that Jenkins noticed occurred during the  middle of 
the night in Indiana – meaning that something produced by the  sun had traveled 
all the way through the Earth to reach Jenkins'  detectors. What could the 
flare 
send forth that could have such an  effect?

Jenkins and Fischbach guessed that the culprits in this bit of  decay-rate 
mischief were probably solar neutrinos, the almost weightless  particles famous 
for flying at almost the speed of light through the  physical world – humans, 
rocks, oceans or planets – with virtually no  interaction with anything.

Then, in a series of papers published in Astroparticle Physics, Nuclear 
Instruments and Methods in Physics Research and Space Science Reviews,  
Jenkins, 
Fischbach and their colleagues showed that the observed  variations in decay 
rates were highly unlikely to have come from  environmental influences on the 
detection systems.

Reason for suspicion
Their findings strengthened the argument that the strange swings in  decay 
rates 
were caused by neutrinos from the sun. The swings seemed to  be in synch with 
the Earth's elliptical orbit, with the decay rates  oscillating as the Earth 
came closer to the sun (where it would be  exposed to more neutrinos) and then 
moving away.

So there was good reason to suspect the sun, but could it be proved?
Enter Peter Sturrock, Stanford professor emeritus of applied physics  and an 
expert on the inner workings of the sun. While on a visit to the  National 
Solar 
Observatory in Arizona, Sturrock was handed copies of the  scientific journal 
articles written by the Purdue researchers.

Sturrock knew from long experience that the intensity of the barrage  of 
neutrinos the sun continuously sends racing toward Earth varies on a  regular 
basis as the sun itself revolves and shows a different face,  like a slower 
version of the revolving light on a police car. His advice  to Purdue: Look for 
evidence that the changes in radioactive decay on  Earth vary with the rotation 
of the sun. "That's what I suggested. And  that's what we have done."

A surprise 
Going back to take another look at the decay data from the Brookhaven  lab, the 
researchers found a recurring pattern of 33 days. It was a bit  of a surprise, 
given that most solar observations show a pattern of  about 28 days – the 
rotation rate of the surface of the sun.

The explanation? The core of the sun – where nuclear reactions  produce 
neutrinos – apparently spins more slowly than the surface we  see. "It may seem 
counter-intuitive, but it looks as if the core rotates  more slowly than the 
rest of the sun," Sturrock said.

All of the evidence points toward a conclusion that the sun is  "communicating" 
with radioactive isotopes on Earth, said Fischbach.
But there's one rather large question left unanswered. No one knows  how 
neutrinos could interact with radioactive materials to change their  rate of 
decay.

"It doesn't make sense according to conventional ideas," Fischbach  said. 
Jenkins whimsically added, "What we're suggesting is that  something that 
doesn't really interact with anything is changing  something that can't be 
changed."

"It's an effect that no one yet understands," agreed Sturrock.  "Theorists are 
starting to say, 'What's going on?' But that's what the  evidence points to. 
It's a challenge for the physicists and a challenge  for the solar people too."

If the mystery particle is not a neutrino, "It would have to be  something we 
don't know about, an unknown particle that is also emitted  by the sun and has 
this effect, and that would be even more remarkable,"  Sturrock said.
Chantal Jolagh, a science-writing intern at the Stanford News Service, 
contributed to this story.



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