J. Geophys. Res., 106, 5721, 2001
Abstract:
A possible ~140 day recurrence in the fluxes and
anisotropies of interplanetary MeV energy protons has previously
been identified in data from the Anisotropy Telescopes
(ATs) on board Ulysses. This measurement was made
during 1998-1999 at a distance from the Sun of
~5 AU. Earlier reports of a 154-day
periodicity in the occurrence rate of solar flares
and other solar activity indicators exist, mainly
for cycle 21 data.
In this paper we compare the ATs measurement, made for
protons in the 1.3-2.2 MeV energy range, with fluxes
of relativistic electrons (~4-10 MeV) and protons
in the range ~30-100 MeV. We consider 5-AU data from
the Ulysses Kiel Electron Telescope (KET) instrument
and 1-AU measurements
from the IMP 8 Cosmic Ray Nuclear Composition
(CRNC) telescope.
We find that at these higher energies significant fluxes
at 5 AU are detected only in correspondence with a
specific feature in the ATs recurrent pattern, thus
supporting the hypothesis of recurrent behavior.
We look for signatures of these events at 1 AU
in the CRNC data and find for all of them an associated
long-duration particle event, regardless of the
longitudinal separation between Ulysses and IMP 8.
Possible solar sources of the events are discussed.
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