DPS 2001 meeting, November 2001
Session 46. Cometary Atmospheres and Solar Wind Interaction
Oral, Chairs: M. Hanner, A. Levasseur-Regourd, Friday, November 30, 2001, 3:00-4:10pm, Regency E

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[46.03] Comet Hyakutake (C/1996 B2): Spectacular Disconnection Event and the Latitudinal Structure of the Solar Wind

J. C. Brandt (U. New Mexico), M. Snow, Y. Yi, C. C. Peterson (LASP/U. Colorado), H. Mikuz (Crni Vrh Obervatory)

Images of comet Hyakutake are analyzed in conjunction with solar wind data from spacecraft (IMP-8 and WIND) to determine the relationship between solar-wind conditions and plasma tail morphology. The disconnection event (DE) on March 25, 1996 is found to be correlated with a crossing of the Heliospheric Current Sheet (HCS). The comet was within 0.1 AU of earth at the time of the DE, and the spacecraft probably experienced the same solar-wind conditions as the comet. Data from the spacecraft show neither high-speed streams, significant density enhancements nor shocks that could have produced the DE as suggested by Wegmann(1995, 2000).

The latitudinal variation in the appearance and orientation of the plasma tail as well as the observations of DEs are interpreted based on results from the Ulysses spacecraft (Brandt & Snow 2000). In the polar solar-wind region, the comet has a relatively undisturbed appearance, no DEs were observed, and the orientation of the plasma tail was consistent with a higher solar-wind speed. In the equatorial solar-wind region, the comet’s plasma tail had a disturbed appearance, a major DE was observed, and the orientation of the plasma tail was consistent with a lower solar-wind speed. The boundary between the equatorial and polar regions crossed by comet Hyakutake in April 1966 was near 30°N (ecliptic) or 24°N (solar) latitude.

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