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The suprathermal population contains a mix of solar wind ions, flare populations, gradual SEP events, pickup ions, and other particle populations (see figure). Since the populations in this mix have distinct histories, suprathermal elemental and charge-state composition are likely to vary with energy (Fisk and Gloeckler 2007), time (Desai et al., 2006a,b) and location. The high initial speeds of suprathermal ions predispose them to efficient injection into acceleration near shocks, making them the ideal seed population for SEPs. Where shocks are quasi-perpendicular, we expect injection energies to be high, and the SEP population should resemble the composition of the higher energy suprathermal ions. Where shocks are quasi-parallel, we expect the SEP composition to reflect the lower energy portions of the suprathermal population. 


Oxygen fluences from ACE measured over a 3-year period (from Mewaldt et al. 2003). Characterization of the suprathermal population Characterize the suprathermal elemental and charge-state composition as a function of energy, time and location. Role of shocks in generating SEPs

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