The pick-up of cometary protons by the solar wind
Altwegg, K.; Balsiger, H.; Goldstein, B. E.; Goldstein, R.; Lazarus, A. J.; Neugebauer, M.
United States, Switzerland
Abstract
The HERS detector of the Ion Mass Spectrometer on the Giotto spacecraft measured the 3-dimensional distribution of picked-up cometary protons over a distance of ≡8 million km upstream of the bow shock of comet P/Halley. The protons were observed to be elastically scattered out of their original cycloidal trajectories such that they were nonuniformly distributed over a spherical shell in velocity space. The shell radius (relative to its expected radius) and thickness increased as the bow shock was approached. Down-stream of the shock, the cometary protons could not be distinguished from the heated solar wind protons.