ANOMALOUS COSMIC RAYS AS PROBES OF MAGNETIC CLOUDS

Abstract

Abstract : We report, for the first time, the observation near the Earth of anomalous cosmic ray (ACR) particles throughout the interiors of interplanetary magnetic clouds (MCs) at the same intensity as outside the MCs. ACRs, accelerated in the outer heliosphere, have unique elemental abundances making their identity unambiguous as they probe these clouds from the outside. Thus, MCs, carried out from the sun by coronal mass ejections (CMEs), are seen to contain no structures that are magnetically closed to the penetration of ions with energies above a few MeV per amu . As the MCs expand outward they must fill their increasing volume with ACRs dynamically, to the same degree as neighboring open field lines. These observations cast doubt on conventional ideas about the closed field topologies of MCs and the cross-field transport of energetic particles. The ACR observations conflict with some reports of significant exclusion from MCs of solar energetic particles (SEPs) of comparable energy and rigidity. A process that allows cross-field transport of ACRs may also allow similar transport of SEPs late in events, causing the large spatial extent and uniformity of SEPs in invariant spectral regions extending far behind the CME-driven shock waves.