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Methanol and hydrogen sulfide in comet P/Halley.
Eberhardt, P.; Meier, R.; Krankowsky, D. +1 more
The Neutral Mass Spectrometer on the Giotto spacecraft measured the gas and ion composition in the coma of comet P/Halley. A detailed model of the ion chemistry inside the contact surface located at 4660 km is used to interpret the measured ion density profiles in the 32 to 35 amu/e mass range. The masses 33 and 35 amu/e are dominated by the proto…
Collimation of cometary dust jets and filaments
Keller, H. U.; Knollenberg, J.; Markiewicz, W. J.
It has been suggested that cometary dust jets, as for example imaged by the Halley Multicolour Camera (HMC), possibly originate from vents, or crater-like surface features. Dust flow emitted from such indentations is collimated if compared to emission from a flat surface. Dust liberated from the bottom of a cometary "crater" emerges at the surface…
Ammonia in comet P/Halley.
Eberhardt, P.; Meier, R.; Krankowsky, D. +1 more
In comet P/Halley the abundances of ammonia relative to water reported in the literature differ by about one order of magnitude from roughly 0.1% up to 2%. Different observational techniques seem to have inherent systematic errors. Using the ion mass channels m/q=19amu/e, 18amu/e and 17amu/e of the Neutral Mass Spectrometer experiment aboard the s…
The induced magnetosphere of comet Halley: Interplanetary magnetic field during Giotto encounter
Neubauer, F. M.; Israelevich, P. L.; Ershkovich, A. I.
Direction of the interplanetary magnetic field (IMF) which governs the orientation of the Halley's magnetosphere was restored by using Giotto magnetic field data. The Giotto trajectory was a twisted curve in the coordinate system rotating with IMF vector and covered rather uniformly the transverse cross section of the comet. Magnetic field vectors…
Abundance and origin of the CH_n_^+^ ions in the coma of comet P/Halley
Altwegg, K.; Balsiger, H.; Geiss, J.
We analyzed data in the mass/charge group 12-16 amu/e from the High Intensity Sensor (HIS) of the Ion Mass Spectrometer IMS on board the spacecraft Giotto during the comet Halley flyby. The most abundant ion in this mass/charge range is CH_3_^+^. Its parent molecules are either CH_2_, CH_3_ or CH_4_. Hereby, the methane abundance serves as an impo…
There is no ``cometopause'' at Comet Halley
Chaizy, P.; Reme, H.; Korth, A. +3 more
Immediately after the flybys at comet Halley by a fleet of spacecraft in 1986, Gringauz et al. (1986a) reported the detection by the Vega-2 spacecraft of a chemical and sharp plasma boundary, which they named the ``cometopause,'' at a distance of ~1.6×105 km from the nucleus. Gringauz and Verigin (1991) presented the ``cometopause'' as …
Shock normal determination for multiple-ion shocks
Coates, A. J.; Neubauer, F. M.; Motschmann, U. +1 more
We have adapted the single-ion Viñas and Scudder (1986) solution to the Rankine-Hugoniot problem to a multiple-ion solution. Using this technique, we can calculate a shock normal direction, shock speed, best estimate of the upstream and downstream magnetic field and plasma asymptotic states, and θBn, the angle between the shock normal a…
The structure of mass-loading shocks. 1. Comets
Neubauer, F. M.; Zank, G. P.; Story, T. R.
A new multifluid model to describe the solar wind-cometary ion plasma in the outer cometary coma is derived. This model is distinguished from previous multifluid models in that wave-particle effects are included explicitly. By considering hydrodynamic timescales, self-consistent dissipative terms (which correspond to the spatial diffusion of comet…
Giotto ion mass spectrometer measurements at comet P/Grigg-Skjellerup
Altwegg, K.; Balsiger, H.; Neubauer, F. M. +6 more
The Giotto ion mass spectrometer high-intensity spectrometer (IMS-HIS) measured fluxes of ions from about 260,000 km before (1008:36 UT spacecraft time) to about 86,000 km after (1701:33 UT spacecraft time) closest approach to comet P/Grigg-Skjellerup during the encounter on July 10, 1992. Although the HIS sensor was not designed to measure proton…
The radial brightness dependence in the dust coma of comet P/Grigg-Skjellerup.
Fulle, M.; Mennella, V.; Colangeli, L. +2 more
In a previous paper (Fulle et al. 1993a) we have obtained a three-dimensional coma model of the short period comet P/Grigg-Skjellerup, by fitting ground-based images taken in coincidence with the fly-by of the GIOTTO spacecraft (GEM mission). Concerning the cometary dust environment, we confirmed the excess of large grains measured by the in-situ …