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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 105, NO. A6,
PAGES 12,579–12,591,
2000
Bidirectional particle flows at cosmic ray and lower (∼ 1 MeV) energies and their association with interplanetary coronal
mass ejections/ejecta
I. G. Richardson
Department of Astronomy, University of Maryland, College Park
V. M. Dvornikov
Institute of Solar-Terrestrial Physics, Irkutsk, Russia
V. E. Sdobnov
Institute of Solar-Terrestrial Physics, Irkutsk, Russia
H. V. Cane
School of Mathematics and Physics, University of Tasmania, Hohart, Tasmania, Australia
Abstract
We demonstrate a close relationship between bidirectional flows of galactic cosmic rays measured by the worldwide neutron
monitor network and bidirectional flows of solar/shock-accelerated particles at much lower energies (∼ 1 MeV) observed by
near-Earth spacecraft, during January–September 1982. We find that ∼ 80% of bidirectional cosmic ray flows are accompanied
by bidirectional low energy ion flows. The observations indicate a close association between BCRFs and interplanetary coronal
mass ejections/ejecta. The bidirectional flows suggest that particles of a wide range of energies are trapped on expanding,
looped magnetic field lines, providing that their gyroradii are much smaller than the ∼ 0.1 to few AU scale sizes of ejecta.
Unidirectional flow components are less well correlated at ∼ 1 MeV and cosmic ray energies, presumably because they reflect
gradients in different particle populations. We discuss several events in detail and illustrate how changes in particle flows
may be related to substructures within these ejecta.
Received 10
September
1999;
accepted 30
January
2000.
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Citation: Richardson, I. G., V. M. Dvornikov, V. E. Sdobnov, and H. V. Cane
(2000),
Bidirectional particle flows at cosmic ray and lower (∼ 1 MeV) energies and their association with interplanetary coronal
mass ejections/ejecta,
J. Geophys. Res.,
105(A6),
12,579–12,591.
Copyright 2000 by the American Geophysical Union.
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