Solar Energetic Particle Production (SEPP) Mission Primary Contacts: Robert P. Lin (UC Berkeley), John L. Kohl (Harvard-Smithsonian CfA) Primary Science Objectives: To understand how solar energetic particles (SEPs) are produced and accelerated in coronal mass ejection (CME) shocks. To understand the role of flare/CME current sheets in the production of SEPs. To understand the physical processes that control SEP production in compact magnetic field regions at the base of the corona. Mission Description: A Near-Sun spacecraft (NSS) in a ~0.25 AU perihelion orbit and a Near-Earth spacecraft (NES) in a geosynchronous or sun synchronous orbit. Launcher: Single LV (e.g., Delta IV Heavy) with dual spacecraft NSS instruments: gamma-ray telescope, hard x-ray telescope, particles and magnetic field detectors, low frequency radio experiment NES instruments: EUV coronagraph/spectrometer, visible light coronagraph/polarimeter, and an EUV disk spectrometer. Investigative Strategy: The following measurements will determine the full range of parameters needed to test and refine all proposed theories for the production of impulsive and gradual SEPs: SEP production in CME shocks: NES instruments determine the CME speed; pre-shock plasma parameters including magnetic field; and suprathermal seed particle energies and densities; the shock’s onset radius, compression ratio, speed, Mach number; post-shock ion and electron densities and velocity distributions, and elemental and charge state composition. NSS instruments determine gamma-ray and x-ray derived SEP energy, number flux and composition at the CME shock site; and in situ SEP properties including charge states after minimum interplanetary transport. SEP production in flare/CME current sheets: NES instruments determine post-flare loop magnetic fields, plasma parameters in current sheets including ion and electron velocity distributions, densities, inflow and outflow velocities, and derived reconnection rates and electric/magnetic field strengths. NSS instruments determine gamma-ray and x-ray derived SEP energy, number flux and composition in the current sheet; and in situ SEP properties including charge states after minimum interplanetary transport. SEP production in compact magnetic field regions: NES instruments determine plasma parameters, magnetic field topology and evolution of magnetic structures over a wide range of sizes, time scales, and temperatures at the coronal base. NSS instruments determine gamma-ray and x-ray derived SEP energy, number flux and compostion in compact magnetic field regions; and in situ SEP properties including charge states after minimum interplanetary transport. Enabling Technologies: Mission can be accomplished with existing technologies. A technical study is needed to further define the mission concept including instrument accommodation, spacecraft concepts, and launch/orbit requirements. Optimization of the high sensitivity gamma-ray instrumentation and hard x-ray focusing optics is needed. Fundamental Science Question: What are the source regions and physical processes controlling the impulsive and gradual production of solar energetic particles.

Solar Energetic Particle Production (SEPP) Mission Primary Contacts: Robert P. Lin (UC Berkeley), John L. Kohl (Harvard-Smithsonian CfA) Relation to NASA Exploration Vision: The resulting new understanding of the physical processes that produce SEPs will provide the detailed physics needed to develop a predictive capability that would give advance warning to protect astronauts and deep space equipment. Relation to NASA Sun-Solar System Connection Science: This mission responds to SSSC Objectives 1) to define the origins and societal impacts of solar variability and 2) to understand fundamental physical processes. The relevant Research Focus Areas are 1) to develop the capability to predict solar activity and the evolution of solar disturbances and 2) to understand how charged particles are accelerated to high energies. Key Result or Science Justification: The key to understanding the production and acceleration of solar energetic particles is to use a quantitative physical description of the plasma, fields, and SEPs at the source regions, together with in situ SEP measurements, to test and refine all proposed theoretical models. Synergism with other Space Missions: These types of measurements will complement those to be made by STEREO, Solar-B, SDO, and upcoming ground-based observatories (e.g. FASER and ATST). Expected Outcome: A new understanding of SEP production leading to a hazard prediction capability. The mission will also provide real-time gamma-ray and in situ SEP data that could be used for hazard warning in lieu of dedicated monitoring.