HR: 1400h
AN: SH23C-05    [Abstracts]
TI: Encounter of Ulysses with Comet McNaught
AU: * Gosling, J T
EM: jack.gosling@lasp.colorado.edu
AF: University of Colorado, 1234 Innovation Drive, Boulder, CO 80303, United States
AU: Neugebauer, M
AF: University of Arizona, Building 92, Tucson, AZ , United States
AU: McComas, D J
AF: Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78225-0510, United States
AU: Goldstein, B E
AF: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA , United States
AU: Skoug, R M
AF: Los Alamos National Laboratory, MS D466, Los Alalmos, NM 87545, United States
AU: Gloeckler, G
AF: University of Maryland, Physics Department, College Park, MD , United States
AU: Zurbuchen, T
AF: University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109, United States
AU: von Steiger, R
AF: International Space Science Institute, Hallerstrasse 6, CH-3012, Bern, Switzerland
AU: Balogh, A
AF: International Space Science Institute, Hallerstrasse 6, CH-3012, Bern, Switzerland
AU: Rees, A
AF: Imperial College, The Blackett Lab., SW7 2BW, London, United Kingdom
AU: Combi, M R
AF: University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109, United States
AB: Comet C/2006 P1 McNaught was the brightest comet observed from Earth in the last 40 years. On February 3, 2007 the comet at a heliocentric distance of ~0.71 AU was nearly radially aligned with the Ulysses spacecraft at a heliocentric distance of ~2.40 AU and at 79 Deg south heliographic latitude. Thus, during a ~4.5-day interval (February 5-9) Ulysses encountered the tail region of this spectacular comet, the region of disturbance in the solar wind produced by the comet being nearly 10 Mkm wide at 2.4 AU. During the encounter the speed of the solar wind dropped from ~750 km/s to a minimum of 360 km/s, the proton density dropped by more than 2 orders of magnitude, and the proton temperature increased from ~1.5x10⁵ to ~4x10⁵ K, while simultaneously very large fluxes of cometary molecular and singly and doubly charged atomic ions were detected. The slowing, depletion and heating of the solar wind proton beam was a result of charge exchange with neutral atoms and molecules in the cometary atmosphere and with the pickup up by the wind of the newly-born cometary ions. Although no shocks were observed during the encounter, the magnetic field strength was slightly enhanced in broad regions at the leading and trailing edges of the tail of the comet and was generally weaker than in the unobstructed solar wind within the heart of the region of interaction. For most of the encounter, the magnetic field direction was nearly radially inward, and thus reversed from its normal outward direction in the southern polar hemisphere at this phase of the present solar cycle. There were, however, shorter periods when the field pointed nearly radially outward, indicating a filamentary structure of the comet tail. One of the intervals of radially outward field coincided with the interval of minimum flow speed and maximum flux of picked up O+ ions.
DE: 2152 Pickup ions
DE: 2199 General or miscellaneous
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Joint Assembly