AGU member since 1987. Associate professor of planetary sciences, University of Arizona. Major area of interest is the physics of space plasmas including high-energy charged-particle acceleration and transport in the heliosphere, and the physics of collisionless shocks. B.A., mathematics, 1985, Fort Lewis College; B.A., physics, 1986, Fort Lewis College; Ph.D., physics, 1991, University of Kansas. Faculty positions as assistant professor, assistant research scientist, and research associate at the Department of Planetary Sciences, University of Arizona, 1993–2007; postdoctoral research associate at Queen Mary College, University of London, 1991–1993. Author/coauthor of 50 papers in refereed journals, 21 in AGU publications. Guest investigator for Voyager and ACE. Currently a member of the steering committee for NSF's SHINE program and a member of NASA's Solar and Heliospheric Physics MOWG. Selected for the NSF Early Career Award, 2004. AGU service as Associate Editor for Geophysical Research Letters, 2001–2003.