Solar Energetic Particle (SEP) Coronal Shock Acceleration: UV Spectro-Imaging Observables

The breakthrough SOHO UVCS observations of a CME-driven shock (Mancuso, et al. 2002, A&A, 383, 267) have opened a new realm of possibilities for remote-sensing measurements of the physical parameters determining the acceleration of SEPs in the solar corona. The UVCS measurement of the non-thermal component of the coronal plasma in response to a CME shock passage provides a direct constraint on SEP shock acceleration in marked contrast to the indirect constraints drawn from correlative temporal and morphological studies. An instrument optimized for these observations and taking advantage of the advances in optics and opto-electronics over the past decade can make measurements providing much stronger constraints on SEP acceleration processes. A summary of the observational constraints potentially obtained by a new generation of instrumentation will be presented. We specifically present calculations of observational requirements for a definitive remote-sensing measurement of the presence and distribution of pre-existing suprathermal seed particles at the site where a CME develops a shock. Seed particles have been invoked in various scenarios over the last thirty years to achieve SEP shock acceleration within timescale constraints defined by prompt energetic particles observed at 1 AU. The necessity of seed particle presence for SEP acceleration is implied but not demonstrated in the correlation measured between the intensity of an SEP event and the occurrence of a fast CME within 24 hours prior to the fast CME associated with the SEP event (Gopalswamy et al. 2004, JGR 109, A12105). The direct observation of the presence and distribution of a coronal suprathermal seed population should resolve this long-standing issue and enable an entirely new SEP predictive capability.