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Detection of cometary pickup ions up to 10 7 km from comet Halley : Suisei observation
Author(s) -
Terasawa T.,
Mukai T.,
Miyake W.,
Kitayama M.,
Hirao K.
Publication year - 1986
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl013i008p00837
Subject(s) - comet , ion , pickup , physics , halley's comet , spacecraft , asymmetry , diffusion , orbit (dynamics) , astronomy , astrophysics , aerospace engineering , quantum mechanics , artificial intelligence , computer science , engineering , image (mathematics) , thermodynamics
Cometary pickup protons were observed as far as 9.7 × 10 6 km away from the cometary nucleus, while the pickup cometary ions of water‐group (expected to be mainly O + ) were observed as far as 4.0 × 10 6 km. Observation of these cometary ions is based on the identification of a specific feature in the phase space distribution of ions (ion‐pickup shell). We found that the pickup shell is usually filled only partially (∼50%). This observation suggests that the efficiency of the energy diffusion is comparable to that of the pitch angle diffusion. From the spatial asymmetry in the cometary ion density observed between inbound and outbound parts of the spacecraft orbit, it is suggested that there was a difference of a factor of 2‐3 between the ion production rates around the inbound and outbound orbit.