Turbulent AGN coronae as the origin of diffuse neutrinos up to PeV energies

Abstract

It has been shown that the turbulence acceleration in AGN coronae can account for 1-10 TeV neutrinos from some AGNs, such as the Seyfert galaxy NGC 1068. Based on this, there are attempts to explain the diffuse neutrinos observed by IceCube with the accumulated contribution from a population of AGNs, but it is found that the maximum neutrino energy is less than tens of TeV, and as a result, additional source classes are needed to explain the high-energy component above this energy. Recently, motivated by the detection of $>100$ TeV neutrinos from the Seyfert galaxy NGC 7469, it was shown that the turbulence acceleration in the corona can explain $>$100 TeV neutrinos given a larger magnetization parameter ($\sigma\sim 1$) in the corona, which leads to a larger maximum proton energy and a hard proton spectrum. In this paper, we extend this assumption to the population of AGNs and study whether the population of AGNs with a wide range of magnetization can explain the entire diffuse neutrino flux. We find that AGN coronae could account for the diffuse neutrinos up to PeV energies if a significant fraction of AGNs have magnetizations as large as $\sigma\sim 1-10$. This conclusion is insensitive to the shape of the magnetization parameter distribution as long as the range of the magnetization parameter is sufficiently wide and the distribution is flat towards high magnetization. Interestingly, this model can also explain the peak of the diffuse neutrino spectrum at $\sim30$ TeV.