I have a degree in Nuclear Medicine, so I am more familiar with decay concepts than many people, and this is news to me too.
I find this utterly fascinating. (Where’s that picture of Spock, now?)
If it truly was some arcane weak nuclear interaction affected by neutrinos (an idea I grasped at in my earlier post) I don’t think there would be a seasonal effect.
The difference between winter and summer is a difference in effective flux on an angled surface. But neutrinos can zip straight through the earth’s crust and not interact with anything.
And it can’t be something like W and Z boson flux from the Sun, because - apart from all the range and lifetime arguments - these massive particles could not be moving at anything like C.
Which makes me think its got to be electromagnetic: some manifestation of the electroweak theory. But this also doesn’t make sense - radioactive decay is not effected by magnetic fields (also heat, gravity etc). That’s why we can trust atomic clocks.
Well I’m stumped.
Here’s my theory.
Changes in the Sun’s magnetic field affect the flux of high energy cosmic rays on the earth. This is a known effect.
Maybe a greater rate of cosmic ray impacts smash up Manganese nuclei in a manner that just happens to look like increased decay, without involving some exotic change to the cross-section of the weak force.