  Large earthquakes occurring worldwide have long been recognised to be non
Poisson distributed, so involving some large scale correlation mechanism, which
could be internal or external to the Earth. Till now, no statistically
significant correlation of the global seismicity with one of the possible
mechanisms has been demonstrated yet. In this paper, we analyse 20 years of
proton density and velocity data, as reported by the ISC-GEM catalogue. We
found clear correlation between proton density and the occurrence of large
earthquakes (M>5.8), with a time shift of one day. The significance of such
correlation is very high, with probability to be wrong less than 10-5. The
correlation increases with the magnitude threshold of the seismic catalogue. A
tentative model explaining such a correlation is also proposed, in terms of the
reverse piezoelectric effect induced by the applied electric field. This result
opens new perspectives in seismological interpretations, as well as in
earthquake forecast.
