Particle and Field Signatures of Coronal Mass Ejections in the Solar Wind

When CME plasma passes over a spacecraft in interplanetary space, it can often be recognized by a number of characteristic signatures in the properties of the plasma and magnetic field. Those signatures are briefly summarized. When two or more signatures are present, they are often not synchronized with each other. As an example, the low-temperature signature is often encountered ahead of the bidirectional streaming of suprathermal electrons. Periods of quiet, nearly radial fields are found in the trailing portions of approximately one quarter of the fast or energetic CME events. It is suggested that the radial fields may be manifestations of the legs of magnetic loops carried into space by the CME. Another feature of the trailing portions of some CME events is a strong flux of outward propagating Alfvén waves. In some events these waves probably represent a return to the ambient solar wind through which the CME is propagating, but we suggest that in other events the waves may be a signature of a transient coronal hole at the footpoints of the CME.