James M. Ryan, Abe Falcone University of New Hampshire, Morse Hall, Durham, NH 03824 USA for Milagro collaboration
The Milagro Gamma Ray Observatory, a ground based water Cherenkov detector designed for measuring very high energy gamma rays, can also be used to study the Sun. Measurement of high energy emission from solar flares will lead to a better understanding of solar energetic particle acceleration, and Milagro, with enhanced data acquisition electronics, will measure solar flare particle emission in the poorly studied energy range from 4 to 300 GeV. Monte Carlo simulations indicate that protons and neutrons in this energy range will be detectable at the ground through the detection of small showers and/or single muons. Milagro can register these events in a scaler counting mode similar to a neutron monitor, and it can also operate in a telescope mode (with a higher threshold energy), thereby greatly reducing background and improving sensitivity. The Milagro prototype, Milagrito, was operated from Feb. 1997 to May 1998 with positive results on the 6 November 1997 GLE. The full-size version of Milagro has recently begun taking data.