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Electron distributions upstream of the comet Halley bow shock: Evidence for adiabatic heating

Anderson, K. A.; Neubauer, F. M.; Glassmeier, K. H. +4 more

We report on three-dimensional plasma electron (22 eV to 30 keV) observations upstream of the comet Halley bow shock, obtained by the RPA-1 COPERNIC (Rème Plasma Analyzer-Complete Positive Ion, Electron and Ram Negative Ion Measurements near Comet Halley) experiment on the Giotto spacecraft. Besides electron distributions typical of the undisturbe…

Comparison of observed and calculated implanted ion distributions outside Comet Halley's bow shock

Coates, A. J.; Neugebauer, M.; Gombosi, T. I. +2 more

This paper compares calculated and measured energy spectra of implanted H⁺ and O⁺ ions on the assumption that the pickup geometry is quasi-parallel and about 1% of the waves generated by the cometary pickup process propagate backward (toward the comet). The model provides a good description of the implanted O⁺ and …

Quasi-linear pitch angle and energy diffusion of pickup ions near comet Halley

Coates, A. J.; Neubauer, F. M.; Johnstone, A. D. +1 more

The process of ion pickup in the environment of Halley's comet is studied in order to see if velocity diffusion driven by the observed level of turbulence can explain the observed development of the implanted ion distribution. The theoretical description used is based on a quasi-linear approach and considers the implantation and transport of comet…

The composition and plasma signature of a large dust impact on the Giotto spacecraft

Coates, A. J.; Balsiger, H.; Neubauer, F. M. +6 more

At about 14,800 km from the comet Halley nucleus, on the inbound leg, at least six of the sensors onboard the Giotto spacecraft observed an unusual, brief (~30 to 500 ms) event: The ion mass spectrometer data show a brief flow of energetic (up to several hundred electron volts) plasma consisting of protons, water group, and heavier ions. The Johns…

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, V_e, from the comet. It is used to calculate the…

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…

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

Erratum: Velocity space diffusion of pickup ions from the water group at comet Halley'' [J. Geophys. Res. 94, 9983 (1988)]

Coates, A. J.; Glassmeier, K. -H.; Wilken, B. +2 more

Velocity space diffusion of pickup ions from the water group at Comet Halley

Coates, A. J.; Glassmeier, K. -H.; Wilken, B. +2 more

We have studied the diffusion in velocity space of cometary ions using the distributions of ions measured by the implanted ion spectrometer on Giotto during the inbound pass. The measurements were transformed into a frame comoving with the solar wind and oriented with the magnetic field. The observations show the evolution of the pitch angle distr…