Sensitivity of neutrino oscillations to the Earth’s interior properties

Understanding the Earth’s deep interior remains challenging, as traditional geophysical methods face ambiguities in linking seismic observations to temperature, composition, or mass density variations. Atmospheric neutrinos, produced by the constant flux of cosmic rays colliding with the upper atmosphere, offer a complementary probe: with energies of a few GeV, they traverse the Earth and experience flavor oscillations influenced by the planet’s electron density distribution, which depends on both its mass density and composition. Combining seismic observations with neutrino measurements in a joint inversion framework could provide complementary constraints on gross spatial and compositional variations in the deep Earth. We consider the next-generation neutrino detectors KM3NeT/ORCA, Hyper-Kamiokande, and DUNE, as well as an idealized hypothetical detector representing the intrinsic sensitivity of the method. The idealized detector is most sensitive to perturbations in the core, whereas realistic detector performance shifts the sensitivity toward the mantle, including the mantle transition zone, where hydrogen enrichment could produce detectable variations in electron density. These results establish the sensitivity of neutrino oscillations to the Earth’s electron density profile and provide a basis for future joint neutrino–seismic tomography.