2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/211113We consider non-standard matter effect in flavor conversion of neutrinos crossing the core of the Earth. We show that oscillation of core crossing neutrinos with $E \gsim 0.5$ GeV can be well described by a first order perturbation theory. We show that due to non-standard matter effect varying chemical composition in the Earth can modify the neutrino flavor conversion by 100%. Effects of CP violating phases in non-standard Neutral Current interactions are emphasized in particular.10 pages, 4 figuresHigh Energy Physics - Phenomenologytext