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Spectral characteristics of low-frequency plasma turbulence upstream of comet P/Halley
Coates, A. J.; Glassmeier, K. -H.; Neubauer, F. M. +4 more
Spectral characteristics of low-frequency plasma turbulence in a cometary environment have been determined using cross-spectral analyses of magnetic field and plasma measurements made on board the Giotto spacecraft upstream of comet P/Halley. Two upstream regions have been identified, where the mean solar wind magnetic field was approximately para…
The velocity distributions of cometary protons picked up by the solar wind
Balsiger, H.; Neubauer, F. M.; Fuselier, S. A. +3 more
Velocity space distributions of picked up cometary protons were measured by the ion mass spectrometer on the Giotto spacecraft upstream of the Halley bow shock. Large pitch angle anisotropies were observed at all distances >1.2×106 km from the comet. As expected, pitch angle diffusion was much more rapid than energy diffusion. When t…
Observations of a shock and a recombination layer at the contact surface of comet Halley
Schwenn, R.; Altwegg, K.; Balsiger, H. +6 more
Observations in the vicinity of the contact surface (ionopause) of comet Halley obtained by the Giotto ion mass spectrometer (IMS) are reported. Two specific events in this region were observed on the inbound pass. Two seconds before the contact surface was encountered, a burst of energized ions (about 20 eV, much greater than thermal energies) wa…
The density of cometary protons upstream of comet Halley's bow shock
Schwenn, R.; Balsiger, H.; Neubauer, F. M. +3 more
Cometary protons picked up by the solar wind were detected by the high energy range spectrometer of the Giotto ion mass spectrometer starting at a cometocentric distance of ~12×106 km. On the average, the density of cometary protons varied approximately as the inverse square of the cometocentric distance, reaching a value of 0.11 cm
The ionopause transition and boundary layers at comet Halley from Giotto magnetic field observations
Neubauer, F. M.
Giotto magnetic field observations at a time resolution of 28.24 vectors per second in the innermost part of the interaction region of comet Halley with the solar wind have yielded the following results: (1) The outer boundary of the cavity, the ionopause, has a thickness of 25 km only, both inbound and outbound, and magnetic field magnitude drops…
Electron impact ionization in the vicinity of comets
Gombosi, T. I.; Cravens, T. E.; Kozyra, J. U. +2 more
The solar wind interacts very strongly with the extensive cometary coma, and the various interaction processes are initiated by the ionization of cometary neutrals. The main ionization mechanism far outside the cometary bow shock is photoionization by solar extreme ultraviolet radiation. Electron distributions measured in the vicinity of comets Ha…