Portal:Radiation astronomy/Resource/9

Neutrons
Around EeV (1018 eV) energies, there may be associated ultra high energy neutrons "observed in anisotropic clustering ... because of the relativistic neutrons boosted lifetime." “[A]t En = 1020 eV, [these neutrons] are flying a Mpc, with their directional arrival (or late decayed proton arrival) ... more on-line toward the source.” From “neutron (and anti-neutron) life-lengths (while being marginal or meaningless at tens of Mpcs)", the growth of their half-lives with energy may naturally explain an associated, showering neutrino halo.

Fairly large fluxes of neutrons have been observed during solar flares such as that of November 12, 1960, with a flux of 30-70 neutrons per cm-2 s-1.

At right is the result of an all Moon survey by the Lunar Prospector using an onboard neutron spectrometer (NS). Cosmic rays impacting the lunar surface generate neutrons which in turn lose much of their energy in collisions with hydrogen atoms trapped within the Moon's surface. Some of these thermal neutrons collide with the helium atoms within the NS to yield an energy signature which is detected and counted. The NS aboard the Lunar Prospector has a surface resolution of 150 km.