Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published 2007 | Published
Book Section - Chapter Open

Cosmic-ray helium intensities over the solar cycle from ACE


Observations of cosmic-ray helium energy spectra provide important constraints on cosmic ray origin and propagation. However, helium intensities measured at Earth are affected by solar modulation, especially below several GeV/nucleon. Observations of helium intensities over a solar cycle are important for understanding how solar modulation affects galactic cosmic ray intensities and for separating the contributions of anomalous and galactic cosmic rays. The Cosmic Ray Isotope Spectrometer (CRIS) on ACE has been measuring cosmic ray isotopes, including helium, since 1997 with high statistical precision. We present helium elemental intensities between ∼10 to ∼100 MeV/nucleon from the Solar Isotope Spectrometer (SIS) and CRIS observations over a solar cycle and compare these results with the observations from other satellite and balloon-borne instruments, and with GCR transport and solar modulation models.

Additional Information

Copyright Universidad Nacional Autónoma de México This work was supported by NASA at GSFC, Caltech, JPL, and Washington University in St. Louis.

Attached Files

Published - 2008-06.pdf


Files (231.7 kB)
Name Size Download all
231.7 kB Preview Download

Additional details

August 19, 2023
October 23, 2023