Collisional effects, ion-acoustic waves, and neutrino oscillations

Abstract

We analyze the role of collisional effects on the coupling between ion-acoustic waves and neutrino flavor oscillations, discussing its relevance for plasma instabilities in extreme plasma environments like in type II supernovae, where intense neutrino bursts exist. Electrons (leptons) are coupled to the electron-neutrino fluid through the weak Fermi force, but the electron-neutrinos are allowed to convert to other neutrino flavors and vice versa. Due to the typically slow frequency of neutrino flavor oscillations, many orders smaller than, e.g., the plasma frequency, an effective energy transfer between plasma waves and neutrino flavor oscillations takes place at the low-frequency electrostatic branch, viz., the ion-acoustic mode. We show the destabilization of ion-acoustic waves in dense astrophysical scenarios, with a focus on the collisional effects mediated by electron-ion scattering. The maximal instability growth-rate is evaluated and compared to the characteristic inverse times of type II supernova explosions. The results can be used for independent experimental verification of the non-zero neutrino mass, in a plasma physics context.