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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…
Giotto IMS measurements of the production rate of hydrogen cyanide in the coma of comet Halley.
Schwenn, R.; Balsiger, H.; Geiss, J. +7 more
The ion composition measurements in the ionosphere of comet Halley by the ion mass spectrometer (IMS) experiment on the Giotto spacecraft are used to estimate the relative abundance of HCN. From a comparison of the normalized number density of ions with mass-to-charge (M/q) ratio of 28 AMU/e with steady-state photochemical models, it can be determ…
Cometary ion flow variations at comet P/Halley as observed by the Giotto IMS experiments.
Schwenn, R.; Balsiger, H.; Ip, W. -H. +5 more
Using the combined data sets from the angle analyzer and the mass analyzer of the Giotto IMS-HIS experiment, the authors have derived the three-dimensional plasma flow properties of cometary ions for masses ≥12 AMU. The results are in agreement with the theoretical model of charge exchange loss of the hot cometary ions.
Particle observations by EPA/EPONA during the outbound pass of Giotto from comet Halley and their relationship to large scale magnetic field irregularities.
Neubauer, F. M.; Ip, W. -H.; Daly, P. +5 more
The acceleration processes producing spikes seen superimposed on the general intensity time profile of energetic particles obtained with EPA/EPONA during the outbound pass of Giotto on 14/15 March 1986, are studied using complementary magnetic field data. Three different types of spikes were identified. Evidence for the ion pick-up process and pro…
Properties of plasma electrons in the magnetic pile-up region of comet Halley.
Anderson, K. A.; Rème, H.; Korth, A. +6 more
In the environment of comet P/Halley, a sharp transition, named the cometopause, was detected by the VEGA and GIOTTO spacecraft around 170000 km from the nucleus. In electron measurements, a clear discontinuity was detected 20% closer to the nucleus, than the cometopause as seen in the ion measurements. Significant changes in the electron distribu…
Evidence for the field line reconnection process in the particle and magnetic field measurements obtained during the Giotto-Halley encounter.
Neubauer, F. M.; Korth, A.; Daly, P. +5 more
Measurements of low (E = 250 - 1000 eV) and high (E = 60 to >300 keV) energy particles as well as the magnetic field obtained during the Giotto-Halley encounter on 13/14 March 1986 are used to study the field line merging process. Strong changes in the pitch angle distribution of energetic ions are observed simultaneously. The observations are …