This seems like it should be taken with a pretty massive grain of salt. The authors' supposed mechanism for this are magnetohydrodynamic interactions between the Earth's dynamo and cosmic rays. I wouldn't believe that without very strong evidence because even very powerful cosmic rays don't penetrate particularly deep into the aesthenosphere. That's why we build dark matter detection facilities in abandoned salt mines: to insulate them from the effects of cosmic rays.

The authors of this study seem to have gotten this by just sifting through datasets searching for correlations. If you look through any large dataset for long enough you're sure to find some 6 sigma correlation in there somewhere.