2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/184034It is shown that the combined action of spin-flavor conversions of supernova neutrinos due to the interactions of their Majorana-type transition magnetic moments with the supernova magnetic fields and flavor conversions due to the mass mixing can lead to the transformation of ν_e born in the neutronization process into their antiparticles \barν_e. Such an effect would have a clear experimental signature and its observation would be a smoking gun evidence for the neutrino transition magnetic moments. It would also signify the leptonic mixing parameter |U_{e3}| in excess of 10^{-2}.LaTex, 25 pages, 3 figures. v4: Discussion section expanded, references added. Matches the published versionHigh Energy Physics - PhenomenologyAstrophysicsHigh Energy Physics - Experimenttext