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L. F. Burlaga (NASA/Goddard Space Flight Center)
There are basically two types of interplanetary ejecta: magnetic clouds and complex ejecta. Magnetic clouds are identified in the solar wind at 1 AU by the passage of a region with strong magnetic field, a smooth rotation in the magnetic field direction through a large angle, and low proton temperatures. Complex ejecta are ejecta that are not magnetic clouds. The simplest magnetic clouds have a flux rope geometry resembling a constant alpha force-free magnetic field. Expansion introduces departures from the simple static model, which become significant at large distances and for slowly moving magnetic clouds. More complicated topologies are also observed (two twisted flux-ropes, disconnected field lines, etc). Magnetic clouds carry significant magnetic helicity away from the Sun. Complex ejecta have no single defining signature. Generally, their proton temperature is low, and often the magnetic field direction varies considerably suggesting tangled fields with little net magnetic helicity. Some complex ejecta are produced by the interaction of two of more CMEs. It will be shown how the interaction can produce evolution from distinct flows to a single entity with no memory of the original source conditions. Magnetic clouds and ejecta can also interact with one another as well as with corotating streams and the plasma sheet. Directions for future observational and theoretical studies will be discussed.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.