HALLEY彗星のION TAILの擾乱とさきがけで観測された太陽風構造(I) : さきがけ磁場観測と太陽圏構造

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In order to study the interaction between the solar wind measured by Sakigake and ion tail disturbances of comet Halley, more than 500 photographs of the comet taken on the ground during this apparition are surveyed. The focus of the present sutdy is the December 31,1985,event, when various types of disturbances occurred, including an outstanding disconnection event (DE)-like knot. Analysis of the Sakigake/IMF data reveals that comet Halley did not encounter the heliospheric neutral sheet on that day, demanding a new explanation for the DE-like event, different from the Niedner-Brandt model. During this event the comet encountered a high-speed solar wind stream from a coronal hole tongue of the sun. The event can be explained by a dynamic pressure model, according to which the DE-like plasmoid was caused by a sudden increase in the dynamic pressure of the solar wind. A result of a computer simulation is found to support this interpretation. The above-stated results were briefly reported already in Geophysical Research Letters. The present work is to report these in detail by separating these into three parts; I, II, and III. (Since different researchers contributed different parts in this detailed work, this is divided into the three parts.) In Part I, the heliospheric structure is obtained from the Sakigake/IMF observation.
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