Summary and Discussion

We presented an analysis of the WIND observations of a magnetic cloud that occurred during interval # 1 of the First IACG Science Campaign from Oct. 18 - 21, 1995. The magnetic field lines in the magnetic cloud had a helical geometry, as one expects for an approximately force-free flux rope. The magnetic field strength profile differed from the prediction of the static constant-alpha model, possibly both because the magnetic cloud was "old" and no longer expanding at 1 AU and because of its interaction with a corotating stream which was overtaking it. A shock was observed ahead of the magnetic cloud, presumably generated by the motion of the magnetic cloud closer to the sun. A second shock was observed inside the magnetic cloud possibly driven by the corotating stream that was interacting with the rear of the magnetic cloud. The interaction region between the magnetic cloud and the corotating stream was complex. There may have been two stream interfaces, one possibly at the rear boundary of the magnetic cloud and a second several hours later.

The observations discussed above suggest many further studies. One class of studies concerns the detailed observations from the WIND spacecraft: e.g., the reasons for the unusual magnetic field strength profile in the magnetic cloud, the nature of the magnetic hole at the front boundary of the magnetic cloud, the properties of the solar wind electrons, the wave activity, the composition of the magnetic cloud and the region between the magnetic cloud and the corotating stream, the sheath ahead of the magnetic cloud, the energetic particles accelerated by the shocks and other processes and their relation to the magnetic cloud, etc. A second class of studies concerns the relations between the observations of WIND and GEOTAIL, which was also in the solar wind; these should provide new insights into the structure of the magnetic cloud, boundaries, filaments, small-scale structures, turbulence, etc. Perhaps the most important class of studies concerns the solar origin of the magnetic cloud and its interaction with the magnetosphere, ionosphere, and thermosphere. The data from IMP and other spacecraft in the magnetosphere will be essential for these studies. A primary motivation for this paper is to provide some basic information needed for these and other studies related to the magnetic cloud.