Measurement of the high-energy gamma-ray emission from the Moon with the Fermi Large Area Telescope

TL;DR

This study measures the Moon's gamma-ray emission spectrum using Fermi-LAT data over 7 years, revealing a correlation with solar activity and enabling the derivation of cosmic-ray spectra near Earth.

Contribution

It provides the first detailed gamma-ray spectrum of the Moon and a comprehensive Monte Carlo model linking cosmic-ray interactions to gamma-ray production.

Findings

Gamma-ray flux correlates with solar activity.

Developed a Monte Carlo simulation of cosmic-ray interactions.

Derived cosmic-ray spectra near Earth from lunar gamma-ray data.

Abstract

We have measured the gamma-ray emission spectrum of the Moon using the data collected by the Large Area Telescope onboard the Fermi satellite during its first 7 years of operation, in the energy range from 30 MeV up to a few GeV. We have also studied the time evolution of the flux, finding a correlation with the solar activity. We have developed a full Monte Carlo simulation describing the interactions of cosmic rays with the lunar surface. The results of the present analysis can be explained in the framework of this model, where the production of gamma rays is due to the interactions of cosmic-ray proton and helium nuclei with the surface of the Moon. Finally, we have used our simulation to derive the cosmic-ray proton and helium spectra near Earth from the Moon gamma-ray data.