Features observed in the trailing regions of interplanetary clouds from coronal mass ejections

ISEE 3 plasma and magnetic field data are used to study features in the trailing regions of interplanetary plasma clouds resulting from coronal mass ejections (CMEs). Approximately one fifth of these events contain periods ≥6 hours for which the interplanetary magnetic field is quiet and nearly radial (|Bx|/B > 0.9). Arguments are presented that the association of quiet radial fields with CMEs is a causal relation, rather than coincidence. The quiet radial fields occur in the trailing, rather than the leading, regions of the CMEs, and they coincide with periods of declining solar wind speed. In some cases the radial field period overlaps periods with other CME signatures, while in other cases the radial field interval follows the disappearance of those signatures. Another trailing‐region feature exhibited by approximately half the CMEs detected by ISEE 3 is a period of outward propagating Alfvén waves. Possible causes of these signatures are discussed.