J. E. Mazur, G. M. Mason, and J. R. Dwyer (all at: Univ. of Maryland, College Park MD 20742; 301-405-4857; mazur@sampx3.umd.edu) T. T. von Rosenvinge and L. F. Burlaga (both at: NASA/Goddard Space Flight Center, Greenbelt, MD 20771)

Solar energetic particles can be used as tracers of the structure of magnetic clouds (e.g. Marsden et al. 1987). Since impulsive flare particles are accelerated within solar flares, their presence inside a magnetic cloud implies that the cloud's magnetic field connects to an active region at the sun.

We report on the fluxes and composition of low energy ions inside 11 magnetic clouds observed with instrumentation on the Wind spacecraft from November 1994 to January 1997. The STEP subsystem of the EPACT experiment on Wind resolves 3He and 4He and the most abundant heavy ion species from ~20 keV/Nucleon to ~1 MeV/Nucleon. Using STEP, we are able to measure the energetic particle composition in an energy range previously unexplored in the context of magnetic clouds.

We will comment on the implications for the large-scale structure of the magnetic field, contrasting the low fluxes of energetic ions observed inside the 10 January 1997 cloud with the 3He-rich population seen inside the 18 October 1995 event.

Marsden R. G. et al. J. Geophys. Res., 92, 11,009-11,019, 1987.