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Dust-acoustic waves in dusty plasmas
Yu, M. Y.; Shukla, P. K.; Rao, N. N.
New acoustic waves originating from a balance of dust particle inertia and plasma pressure are investigated. It is shown that these waves can propagate linearly as a normal mode in a dusty plasma, and non-linearly as supersonic solitons of either positive or negative electrostatic potential.
From Interstellar Dust to Comets: A Unification of Observational Constraints
Greenberg, J. Mayo; Hage, J. I.
The interstellar dust model of comets is numerically worked out to satisfy simultaneously several basic constraints provided by observations of Comet Halley, and to derive the porosity of coma dust. The observational constraints are (1) the strengths of the 3.4 and 9.7 micron emission bands, (2) the shape of the 9.7 micron band, (3) the amount of …
Determination of comet Halley gas emission characteristics from mass loading of the solar wind
Coates, A. J.; Johnstone, A. D.; Huddleston, D. E.
We set out to fit the velocity profile of the solar wind during Giotto's approach to comet Halley with the mass loading produced by a simple model of the neutral particle distribution. The model assumes a constant gas production rate, Q, ionization rate, ν, and a radial expansion velocity, Ve, from the comet. It is used to calculate the…
Attogram Dust Cloud a Million Kilometers from Comet Halley
Kissel, Jochen; Utterback, Nyle G.
Particle-impact ion mass spectrometers carried on the Giotto and two Vega spacecraft missions to Comet Halley in 1986 produced unexpected signals almost one million kilometers from Halley which can be attributed to high number densities of dust particles with masses of order 10 to the -18 g. The data imply that up to several percent of the total m…
Bulk properties and velocity distributions of water group ions at comet Halley: Giotto measurements.
Coates, A. J.; Glassmeier, K. -H.; Wilken, B. +3 more
In the region upstream of comet Halley, pickup heavy ions of cometary origin were directly observed by the Implanted Ion Spectrometer on Giotto. Here the authors discuss diffusion of this population in pitch angle and in energy, during the approach to the comet and on the outbound leg. The two data sets are compared and qualitative ideas on scatte…
Plasma parameters near the Comet Halley bow shock
Coates, A. J.; Wilken, B.; Kessel, R. L. +2 more
Plasma data from the Johnstone Plasma Analyzer on Giotto are used in a Rankine-Hugoniot analysis of Comet Halley bow shocks. The shock normals are obtained and compared with models and other estimates. Proton bulk parameters from the Fast Ion Sensor inbound are analyzed, and water group densities from the Implanted Ion Sensor (IIS) are obtained wh…
The Identification of H 3S + with the Ion of Mass per Charge (m/q) 35 Observed in the Coma of Comet Halley
Reme, H.; Korth, A.; Lin, R. P. +3 more
A sharp peak in the mass spectrum at 35 amu is observed by the heavy ion analyzer on board the Giotto spacecraft just inside the ionopause. This peak is identified with H3S(+) and it is argued that the dominant source of its likely parent molecule (H2S) is the observed distributed source of circumnuclear dust, rather than the central nucleus. In t…
Comparison of picked-up protons and water group ions upstream of comet Halley's bow shock
Coates, A. J.; Neubauer, F. M.; Neugebauer, M.
Data are presented on the properties of picked-up cometary protons and water group (WG) ions observed upstream of the bow shock of comet Halley by the ion mass spectrometer and Johnstone plasma analyzer experiments on the Giotto spacecraft. The number of WG ions exceeded the number of cometary protons at cometocentric distances r<1.3×106
Giotto magnetic field observations at the outbound quasi-parallel bow shock of comet Halley.
Coates, A. J.; Neubauer, F. M.; Glassmeier, K. H. +4 more
The investigation of the outbound bow shock of comet Halley using Giotto magnetometer data leads to the following results: the shock is characterized by strong magnetic turbulence associated with an increasing background magnetic field and a change in direction by 60° as one goes inward. The thickness of the quasi-parallel shock was 120000 km. The…
Interpretation of the inner coma observations of comet P/Halley by the Halley Multicolour Camera.
Keller, H. U.; Thomas, N.
The brightness dependence with distance of the inner coma of comet P/Halley, as observed by the Halley Multicolour Camera on board Giotto, shows 3 distinct regions. From about 400 - 2000 km from the nucleus, deviations from a z-1 law are evident where z is the distance from the nucleus centre. Fountain model calculations indicate that s…