We report on abundance measurements of 10Be, 26Al, 36Cl, and 54Mn in the Galactic cosmic rays (GCRs) using the Cosmic-Ray Isotope Spectrometer (CRIS) instrument aboard the Advanced Composition Explorer spacecraft at energies from D70 to D400 MeV nucleon~1. We also report an upper limit on the abundance of GCR 14C. The high statistical signiÐcance of these measurements allows the energy dependence of their relative abundances to be studied. A steady-state, leaky-box propagation model, incorporating observations of the local interstellar medium (ISM) composition and density and recent partial fragmentation cross section measurements, is used to interpret these abundances. Using this model, the individual galactic conÐnement times derived using data for each species are consistent with a unique conÐnement time value of Myr. The CRIS abundance measurements are consis-q esc \ 15.0^1.6 tent with propagation through an average ISM hydrogen number density H atoms n H \ 0.34^0.04 cm~3. The surviving fractions, f, for each radioactive species have been calculated. From predictions of the di †usion models of Ptuskin & Soutoul, the values of f indicate an interstellar cosmic-ray di †usion coefficient of D \ (3.5^2.0) ] 1028 cm2 s~1.

The IMPACT (In situ Measurements of Particles And CME Transients) investigation on the STEREO mission was designed and developed to provide multipoint solar wind and suprathermal electron, interplanetary magnetic field, and solar energetic particle information required to unravel the nature of coronal mass ejections and their heliospheric consequences. IMPACT consists of seven individual sensors which are packaged into a boom suite, and a SEP suite. This review summarizes the science objectives of IMPACT, the instruments that comprise the IMPACT investigation, the accommodation of IMPACT on the STEREO twin spacecraft, and the overall data products that will flow from the IMPACT measurements. Accompanying papers in this volume of Space Science Reviews highlight the individual sensor technical details and capabilities, STEREO project plans for the use of IMPACT data, and modeling activities for IMPACT (and other STEREO) data interpretation.

We report measurements of record-setting intensities of cosmic-ray nuclei from C to Fe, made with the Cosmic Ray Isotope Spectrometer carried on the Advanced Composition Explorer in orbit about the inner Sun-Earth Lagrangian point. In the energy interval from ∼70 to ∼450 MeV nucleon −1 , near the peak in the near-Earth cosmic-ray spectrum, the measured intensities of major species from C to Fe were each 20%-26% greater in late 2009 than in the 1997-1998 minimum and previous solar minima of the space age (1957-1997). The elevated intensities reported here and also at neutron monitor energies were undoubtedly due to several unusual aspects of the solar cycle 23/24 minimum, including record-low interplanetary magnetic field (IMF) intensities, an extended period of reduced IMF turbulence, reduced solar-wind dynamic pressure, and extremely low solar activity during an extended solar minimum. The estimated parallel diffusion coefficient for cosmic-ray transport based on measured solar-wind properties was 44% greater in 2009 than in the 1997-1998 solar-minimum period. In addition, the weaker IMF should result in higher cosmic-ray drift velocities. Cosmic-ray intensity variations at 1 AU are found to lag IMF variations by 2-3 solar rotations, indicating that significant solar modulation occurs inside ∼20 AU, consistent with earlier galactic cosmic-ray radial-gradient measurements. In 2010, the intensities suddenly decreased to 1997 levels following increases in solar activity and in the inclination of the heliospheric current sheet. We describe the conditions that gave cosmic rays greater access to the inner solar system and discuss some of their implications.

cles over a very broad energy range, as well as coordinated management, science operations, data processing, and scientific analysis. Together, ISIS observations allow us to explore the mechanisms of energetic particles dynamics, including their: (1) Originsdefining the seed populations and physical conditions necessary for energetic particle acceleration; (2) Acceleration-determining the roles of shocks, reconnection, waves, and turbulence in accelerating energetic particles; and (3) Transport-revealing how energetic particles propagate from the corona out into the heliosphere. The two ISIS Energetic Particle Instruments measure lower (EPI-Lo) and higher (EPI-Hi) energy particles. EPI-Lo measures ions and ion composition from ∼20 keV/nucleon-15 MeV total energy and electrons from ∼25-1000 keV. EPI-Hi measures ions from ∼1-200 MeV/nucleon and electrons from ∼0.5-6 MeV. EPI-Lo comprises 80 tiny apertures with fields-of-view (FOVs) that sample over nearly a complete hemisphere, while EPI-Hi combines three telescopes that together provide five large-FOV apertures. ISIS observes continuously inside of 0.25 AU with a high data collection rate and burst data (EPI-Lo) coordinated with the rest of the SPP payload; outside of 0.25 AU, ISIS runs in low-rate science mode whenever feasible to capture as complete a record as possible of the solar energetic particle environment and provide calibration and continuity for measurements closer in to the Sun. The ISIS Science Operations Center plans and executes commanding, receives and analyzes all ISIS data, and coordinates science observations and analyses with the rest of the SPP science investigations. Together, ISIS' unique observations on SPP will enable the discovery, untangling, and understanding of the important physical processes that govern energetic particles in the innermost regions of our heliosphere, for the first time. This paper summarizes the ISIS investigation at the time of the SPP mission Preliminary

The cosmic-ray proton and helium spectra from 0.2 GeV nucleon~1 to about 200 GeV nucleon~1 have been measured with the balloon-borne experiment Isotope Matter-Antimatter Experiment (IMAX) launched from Lynn Lake, Manitoba, Canada, in 1992. IMAX was designed to search for antiprotons and light isotopes using a superconducting magnet spectrometer together with scintillators, a time-of-Ñight system, and Cherenkov detectors. Using redundant detectors, an extensive examination of the instrument efficiency was carried out. We present here the absolute spectra of protons and helium corrected to the top of the atmosphere and to interstellar space. If demodulated with a solar modulation parameter of / \ 750 MV, the measured interstellar spectra between 20 and 200 GV can be represented by a power law in rigidity, with (1.42^0.21) ] 104R~2.71B0.04 (m2 GV s sr)~1 for protons and (3.15^1.03) ] 103R~2.79B0.08 (m2 GV s sr)~1 for helium. Subject headings : cosmic rays È elementary particles È ISM : abundances