Title: Detecting the Origin of Shock-Accelerated Solar Energetic Particles Short Title: Sources of SEPs Author: A. Vourlidas (NRL) Update History: Feb-24-09: Draft #1 Participating Instruments: SOHO/LASCO (POC: G. Stenborg, guillermo.a.stenborg (at)nasa.gov) STEREO/SECCHI (POC: S. Plunkett, simon.plunkett (at) nrl.navy.mil) Scientific Objective: To determine the time and site of injection of SEPs accelerated at CME-shocks. Scientific Justification: There is an ongoing debate about the origin of the energetic particles that accompany large CME/flare events. While both CMEs and flares can accelerate particles, the fraction of the two populations in a given SEP event is currently very difficult to determine. The problem arises from uncertainties about the location and time of formation of the CME shock, the injection time and propagation path of the particles, and the magnetic connectivity between the flare site and the CME. Previous work has shown that the shock-accelerated particles must originate from shock heights of 2-10 Rs and their injection time has an accuracy of 1-2 minutes. Nothing concrete is known about the connectivity of the flare to the CME and in particular about its evolution with time. With SOHO, we could localize the CME shock with an accuracy of about 10-12 min (1/2 of the standard C2 cadence) if it occurs below 6 Rs, and twice less if it occurred in the C3 field of view. With the synoptic SECCHI program, we can improve this accuracy to about 6 min. It is not know, though, how the shock front evolves with time and what is its 3D shape and location In this JOP, we seek to improve the situation by following the evolution of both the CME--driven shock and the associated active region from multiple viewpoints and with high cadence using the EUV imagers and white light coronagraphs aboard SOHO and STEREO. To achieve this we will observe an active region with SEP potential (e.g., complex photospheric field, active CME producer) for about a week while it crosses Earth and STEREO-A connected longitudes (~50deg to 140deg West). Operational Considerations: The observations will be run as a Target of Opportunity when an active region with SEP potential approaches 50 deg West. The evaluation of the SEP potential of the target will be done by monitoring its activity in the STEREO-B and SOHO images and a decision will be made once it crosses the central meridian (as viewed form Earth). The requested observing programs are: SOHO/LASCO: C2 full-res at 8 min cadence, C3 at 20 min cadence, EIT half-res SECCHI/EUVI: 195A-centric synoptic in SSR1, 195A SEP-optimized in SSR2 SECCHI/CORs: no changes The JOP should be run multiple times until several events are recorded. We anticipate to optimize in the observing programs as we go along based on the lessons learned from the past observations. This JOP should be in place and ready to run as soon as possible to be prepared for the upcoming rise in solar activity. Notes: This JOP may be augmented with HINODE/EIS observations. The discussions with the EIS team about the best observing program are under way. We'll update this JOP if such observations become feasible.