Time Variations of the Modulation of Anomalous and Galactic Cosmic Rays
E.R. Christian, T.T. von Rosenvinge
NASA/Goddard Space Flight Center, Greenbelt, MD, USA
C.M.S. Cohen, A.C. Cummings, J.S. George, R.A. Leske, R.A. Mewaldt, E.C. Stone
California Institute of Technology, Pasadena, CA, USA
P.L Slocum, M.E. Wiedenbeck, N. Yanasak
Jet Propulsion Laboratory, Pasadena, CA, USA
W.R. Binns, P.L. Hink, J. Klarmann, M. Lijowski
Washington University, St. Louis, MO, USA
Since the start of solar cycle 23 in 1997, the intensities of galactic
rays at 1 AU have dropped by more than 30%, and the anomalous cosmic rays
have decreased by an even larger amount. The instantaneous level of modulation
is a combination of short-term "Forbush decreases" and the long-term solar
cycle. The large collecting power and high resolution of the Cosmic Ray
Isotope Spectrometer (CRIS) and the Solar Isotope Spectrometer (SIS)
instruments on the Advanced Composition Explorer (ACE) allow us to investigate
the changing modulation on short time scales and at different rigidities.
With these data, we will study the differences between the short term and long
term effects and the correlation of these effects with magnetic field, current
sheet tilt angle, and other phenomena.