Interaction of the Magnetic Cloud and a Corotating Stream

An apparent stream interface, which might correspond to the rear boundary of the magnetic cloud, was observed at 292.954 behind a region of high density and strong magnetic fields (see Figure 1). There appears to be a second stream interface at 293.245 following a second enhancement in intensity. The presence of two enhancements is unusual, and should accounted for in a more detailed analysis of this event. Large directional discontinuities were observed in the region between these two interfaces. This region is unusual, but its nature cannot be determined from the observations considered here. One possibility is that a compound stream followed the magnetic cloud and the two stream interfaces correspond to the two corotating streams. A second possibility is that a corotating stream was interacting with the heliospheric plasma sheet, in which case the multiple directional discontinuities might represent crossings of the heliospheric current sheet. A third possibility is that a single corotating stream interacted with the magnetic cloud producing an instability that formed a complex boundary. A fourth is that the corotating stream interacted with the wake of the magnetic cloud. Multispacecraft studies, the analysis of composition, detailed studies of the discontinuities, the observations of energetic particles, and solar observations might help to define the nature of the interaction. These studies will require the combined efforts of many people and are beyond the scope of this brief paper.