In fact, not just solar flares, but any solar activity seems to have an effect on how quickly radioactive isotopes decay.
"All of the evidence points toward a conclusion that the sun is 'communicating' with radioactive isotopes on Earth."
But they don't know how, and learning the answer to that question will be very, VERY interesting.
Their current thinking is "neutrinos" but considering that a neutrino can pass through a light year of lead without being absorbed it doesn't make a lot of sense.
This might be a way to check the neutrino theory.
For damn sure, solving this riddle will mean some new additions to our understanding of physics. That's always good.