Astrophysical Fluxes as Windows into the Nature of Neutrinos

Neutrinos permeate the Universe, possessing energies from the meV scale all the way up to EeVs, and potentially beyond. The abundance and variety of these neutrino fluxes makes them excellent candidates for experimentally probing the fundamental nature and behaviour of neutrinos. In this thesis, we will assess how neutrinos produced in two very different astrophysical environments can be used for this purpose. We will begin by looking at how the pseudo-Dirac scenario for neutrino masses would impact the observations of Solar neutrinos at the future JUNO experiment. It will be shown that these effects can be sizeable, and used to constrain the parameter space of this scenario. Our focus will then shift to point sources of neutrinos at the IceCube experiment. We will model the effects of interactions between these high energy neutrinos, and the relic neutrinos left over from the early Universe. Using public experimental data, we will then place constraints on both the density of relic neutrinos, and the parameters of a new, scalar mediated, interaction between neutrinos.