Production and detection of an axion dark matter echo
Electromagnetic radiation with angular frequency equal to half the axion mass stimulates the decay of cold dark matter axions and produces an echo, i.e. faint electromagnetic radiation traveling in the opposite direction. We propose to search for axion dark matter by sending out to space a powerful beam of microwave radiation and listening for its echo. We find that this is a promising approach to axion detection in the 2×10^(-7) to 3×10^(-4) eV mass range.