HR: 0830h
AN: SH11C-1127    [PDF]
TI: Ulysses Observations of Short-Period ($<$30 days) Modulation in Galactic Cosmic Rays
AU: * Slocum, P L
EM: penny.l.slocum@aero.org
AF: Space Sciences Department The Aerospace Corporation, 355 S. Douglas Ave., El Segundo, CA 90245 United States
AU: Blake, J B
AF: Space Sciences Department The Aerospace Corporation, 355 S. Douglas Ave., El Segundo, CA 90245 United States
AU: Krupp, N
AF: Max-Planck Institut fuer Aeronomie, Str. 2, Katlenburg-Lindau, D-37191 Germany
AU: Keppler, E
AF: Max-Planck Institut fuer Aeronomie, Str. 2, Katlenburg-Lindau, D-37191 Germany
AU: Franz, M
AF: Max-Planck Institut fuer Aeronomie, Str. 2, Katlenburg-Lindau, D-37191 Germany
AB: Earlier a frequency analysis was carried out of the short--period GCR modulation as seen by Ulysses (EPAC, KET) for the time period from December 1993 to May 1994 (Blake et al. GRL 24, 671, 1997). During the five month period, the modulation of GCR protons with E$>$230 MeV was not the usual 26 days but more than 29 days, and the CIR--associated $\sim$MeV ions did not exhibit this period shift. Using data from the Energetic Particle Composition (EPAC) instrument on Ulysses, we have searched for other intervals in which the short period modulation of the GCRs deviates from its average value of $\sim$26 days. The data examined in this study were acquired between January 1992 and December 2001. Using more than one algorithm, we have derived frequency spectra from the data and have compared the results. We have also examined the behavior of the CIR--associated $\sim$MeV He flux from EPAC during the same time periods. Finally, we have looked for periodicity in the ratios of GCR proton fluxes from the 4 telescopes in the EPAC detector. We discuss the implications of the combined results from each of these analyses. This work was supported at The Aerospace Corporation by JPL under contract 958748 and at MPAe by the Max--Planck--Gesellschaft zur F\"orderung der Wissenschaften e.V.
DE: 2104 Cosmic rays
DE: 2114 Energetic particles, heliospheric (7514)
DE: 7514 Energetic particles (2114)
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting