This grant supports the continued operation and analysis of data from cosmic ray neutron detectors at South Pole and McMurdo, Antarctica. The neutrons which reach the surface are produced by cosmic rays in the upper reaches of the Earth's atmosphere. The variation of the neutron flux in time is caused by turbulence and shock waves in the interplanetary medium, which in turn, is effected by solar activity. Occasionally solar flares produce protons with sufficient energy to reach the Earth's surface and the detector at South Pole is the most sensitive on Earth to these so- called ground level enhancements (GLE's). The study of GLE's can reveal details about solar flares and their impact on the Earth's environment.
