γ-ray and ultra-high energy neutrino background suppression due to solar radiation

Shyam Balaji

Submitted on 7 November 2022


The Sun emits copious amounts of photons and neutrinos in an approximately spatially isotropic distribution. Diffuse γ-rays and ultra-high energy (UHE) neutrinos from extragalactic sources may subsequently interact and annihilate with the emitted solar photons and neutrinos respectively. This will in turn induce an anisotropy in the cosmic ray background due to attenuation of the γ-ray and UHE neutrino flux by the solar radiation. Measuring this reduction, therefore, presents a simple and powerful astrophysical probe of electroweak interactions. In this letter we compute such anisotropies, which at the Earth (Sun) can be 2×103(0.5)% and 1×1016(2×1014)% for TeV scale γ-rays and PeV scale UHE neutrinos respectively. We briefly discuss exciting observational prospects for experiments such as the Fermi Gamma-Ray Space Telescope Large Area Telescope (Fermi LAT), High Energy Stereoscopic System (H.E.S.S), High-Altitude Water Cherenkov (HAWC) detector and IceCube. The potential for measuring γ-ray attenuation at orbital locations of other active satellites such as the Parker Solar Probe and James Webb Space Telescope is also explored.


Comment: 6 pages, 3 figures

Subjects: Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Solar and Stellar Astrophysics; High Energy Physics - Phenomenology


Annihilation cross sections in units of $\mu$b for $\gamma\gamma$ (cyan) and resonant $\nu\bar{\nu}$ (blue) as function of the incident $\gamma$-ray or ultra-high energy neutrino respectively. We take $E_{\gamma\odot}=0.5$eV and $E_{\nu\odot}=0.53$MeV since these are typical energies for photons and neutrinos being emitted by the Sun.