Acceleration of heavy ions at CME-driven Interplanetary Shocks Near Earth

Interplanetary (IP) shocks driven by coronal mass ejections (CMEs) are known to accelerate ions up to 10s of MeV in energy. Since the CMEs and their shocks propagate through the ambient solar wind, it was generally believed that their seed particles originate from the solar wind. However, advanced composition instruments such as the Ultra Low-Energy Isotope Spectrometer (ULEIS) and the Solar Energetic Particle Ionic Composition Analyzer (SEPICA) on board NASA's Advanced Composition Explorer (ACE) have shown that a substantial fraction of such CME-driven IP shocks accelerate tracer ions like 3He and He+ that are extremely rare in the thermal solar wind plasma. Since both these species are relatively more abundant in the energy region between ~2-100 keV/nucleon, their mere presence in the accelerated populations points to an origin in the suprathermal tail. In this presentation, we will survey the ACE/ULEIS, ACE/SEPICA measurements between November 1997 and October 2000 and identify all CME-driven IP shocks that accelerated both 3He and He+ ions. We will compare the measurements of these rare ion species with those of the more common heavier ions from C-Fe. We will perform detailed case studies of individual events along with a comprehensive statistical survey and investigate the ion injection and acceleration efficiencies as a function of their mass-to- charge (M/Q) ratio. We will also compare properties of the accelerated ions with the locally measured shock strength parameters.