Research Interests:

Astrophysics (gamma-ray astronomy), solar flare particle acceleration, gamma-ray detector development.

Particle acceleration phenomena occur in astrophysical plasmas at many sites in the universe. Understanding the accelerating mechanisms is a fundamental problem in astrophysics that is studied by observing radiation that reaches the Earth, including charged particles, neutrons, and the full range of the electromagnetic spectrum. Solar flares provide a rich source of observational data showing that protons are sometimes accelerated to energies as high as 30 GeV within a possible time scale of seconds. The solar particle acceleration mechanisms are most probably operative in other plasma environments.

My research utilizes the data obtained from X-ray and g-ray spectrometers carried aboard Earth-orbiting satellites. The Solar Maximum Mission's satellite Gamma Ray Spectrometer (GRS), which observed about 250 solar flares with energetic photon emissions above 300 keV in a 10-year period, contains a particularly valuable database. Several events show neutron emission >50 MeV. The g-ray and neutron results bear directly on the properties of the accelerated particles. This information, when correlated with radio, optical, and X-ray emissions from the same flare, gives further insight into the flare acceleration process. We also use the g-ray data from balloon and satellite experiments to study high-energy phenomena in cosmic sources. Part of my research activities focus on developing new means to detect g-rays, technology upon which future advances in the field will rely. I am also peripherally interested in developing instruments to record g-rays from natural radioactivity (radon) and from nuclear fallout trapped in glaciers.

My research involves collaboration with colleagues at the University of New Hampshire and with several U.S. and international institutions. My collaborations with scientists and students at the Max-Planck-Institute for Extraterrestrial Physics (Garching) and the University of Bern and the Paris Observatory (Meudon) have resulted in several recent publications.

Former graduate students have found faculty positions at other universities and research positions at several federal laboratories and with university research groups. New graduate students may participate in ongoing and future programs.