Abstract To investigate if O+ ions originating from parent molecules of comet Halley can produce the ion fluxes observed at 28 × 106 km upstream of the comet on March 25, 1986, possible processes to produce high speed O atoms from a cometary nucleus are studied. It is found that O atoms dissociated from H2O and CO have average terminal speeds of ∼ 2.5 km s−1 and 3.4∼3.7km s−1 respectively. These O atoms cannot reach the ICE spacecraft at 28 × 106 km from Halley because of their low speeds. Oxygen atoms dissociated from CO2 in a two-step process can have speeds up to 9.1 km s−1 so that a fraction of the O atoms may be able to reach ICE on March 25. These O atoms can produce O+ ion flux of about 0.02 ion cm−2 s−1, at 28×106 km upstream of the comet, in the energy range of 80 to 160 Kev with the solar wind speed of 500 to 700 km s−1. The calculated O+ ion flux is 4 orders of magnitude smaller than the observed fluxes of ∼ 100 ions cm−2 s−1. Therefore it is very difficult to explain the observed energetic ion fluxes by ions of cometary origin.
On the origin of the ions at 28 million kilometers upstream of comet Halley
Advances in Space Research ; 9 , 3 ; 355-358
1989-01-01
4 pages
Article (Journal)
Electronic Resource
English
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