The rotation of Earth?
The 24 hour variation works against the idea that solar neutrinos are the active agent in variation in the radioactive decay constant. The mass of the earth should have no effect on neutrino flux. The agent that is producing this variation is attenuated by the mass of the earth. Solar flares have been shown to effect the radioactive decay constant greatly.
There is some factor produced by both solar flares and the general solar reaction in general that are influencing the radioactive decay constant. I would venture to guess that this factor is magnetic in nature.
To test this posit, place the LENR reactor in a magnetically shielded box and see if the effect related to a changing radioactive decay constant is eliminated or reduced.