Observations of the Solar Wind and Cometary Ions during the Encounter Between Giotto and Comet Grigg-Skjellerup
Coates, A. J.; Winningham, J. D.; Borg, H.; Amata, E.; Gurgiolo, C.; Wilken, B.; Jockers, K.; Johnstone, A. D.; Huddleston, D. E.
United Kingdom
Abstract
The solar wind interaction with the outfiowing gas from a second comet has been recorded by the same in-situ instrumentation that was used for the comet Halley encounter m 1986. The new comet, Grigg-Skjellerup, is the smallest so far observed since the size of the interaction region is comparable with a cometary ion gyroradius Preliminary results show that there is much in common with the larger comet and that the most obvious differences lie in the degree to which the velocity space diffusion of the cometary ions has developed. Surprisingly despite the small scale, there are several apparent boundaries in the flow which are similar to those at Halley. More detailed analysis is required to determine the nature of the boundaries and to reveal any other differences due to the small scale. We obtain a gas production rate of 7.5 ± 1.5 × l027 water group molecules s-1 for the comet.