WIND OBSERVATIONS OF ENERGETIC IONS FAR UPSTREAM OF THE EARTHS BOW-SHOCK

During the first year of operation, the WIND spacecraft followed a com plicated orbit which took it from the Earth to the upstream libration point and back again. During this time, a considerable number of upstr eam particle events were observed all the way out to the libration poi nt. These events are typically of short duration (a few tens of minute s) and up until now have only been seen in the energetic protons (at e nergies of a few tens of keV, but extending up to several hundreds of keV). We present here new observations from the Three-dimensional (3D) plasma and energetic particle experiment on the WIND spacecraft of th ese upstream events, with particular emphasis on the uniqueness of the observations from this instrument: energy spectra measured over the r ange from a few keV to several hundreds of keV, and complete three-dim ensional angular distributions covering the same range of energies. We present here for the first time a complete spectrum of these ions ext ending from a few eV to a few MeV. This spectrum, with a turnover at o ne or two keV, shows that the bulk of the energy density of the upstre am ions is at around 1 keV. These are most likely the particles respon sible for the low-frequency waves which are usually seen accompanying upstream events.