High-energy neutrinos from a lunar observatory

The detection of high-energy (HE) cosmic and solar-flare neutrions near the lunar surface would be feasible at energies much lower than for a terrestrial observatory. At these lower energies ( 10 to the 9th eV), the neutrino background is drastically reduced below that generated by cosmic rays in the Earth's atmosphere. Because of the short mean free path ( 1m) of the progenitor pi and K mesons against nuclear interactions in lunar rocks, the neutrino background would be quite low. At 1 GeV, less than 1% of the pions would decay; at 10 GeV, 0.1%. Thus, if the neutrino flux to be observed is intense enough, and its spectrum is steep enough, then the signal-to-noise ratio is very favorable. The observation of HE neutrinos from solar flares would be dramatically enhanced, especially at lower energies, since the flare spectra are very steep. Detection of these neutrinos on Earth does not appear to be feasible. A remarkable feature of solar flares as viewed in HE neutrinos from a lunar base is that the entire surface of the Sun would be visible.