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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…

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