Bidirectional particle flows at cosmic ray and lower (∼1 MeV) energies and their association with interplanetary coronal mass ejections/ejecta

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.