Computer Science
Scientific paper
Jul 1989
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989mst..........1v&link_type=abstract
MsT. Thesis, USP, Brazil, 134 pages, (1989)
Computer Science
2
Comet P/Halley, Comets, Cometary Instabilities
Scientific paper
280 photographic images of Comet Halley were obtained in CNPq/LNA from September 26, 1985 to July 10, 1986. 45 of them refer to the epoch of the opposition of November 18, 1985. The last ones were analysed on the PDS 1010A Microdensitometer, at CNPq/ON, and the digital treatment disclosed the presence of structures with dimensions from 103 to 104 km in the inner coma, at projected cometocentric distances from 4.1 x 103 to 6 x 104 km. Such structures were interpreted as diamagnetic cloudlets of cometary ions moving in the sub-solar hemisphere of the coma, to the tailwards. It is proposed that these cloudlets are the result from the mirror instability, suffered by the just captured ions by the magnetic field from solar wind, and whose perpendicular kinetic energy to the field is bigger than the parallel. It is proposed also that the rays should be originate from the compression of these cloudlets on contact surfaces, where the solar wind becomes stagnant.
The remaining 235 photographs were analysed through visual inspection of projected images and also through photographic processing, for the mentioned Microdensitometer was inoperative on the dates which were reserved for by the National Observatory, Rio de Janeiro. The structures seen in the plates of the opposition, interpreted as diamagnetic ions cloudlets, were recognized and confirmed. Detached arches from the nucleus could be detected in several plates. They seem to be rays in formation, resulting from the diamagnetic ion cloudlets compression against the magnetic barrier built by the friction of neutral molecules ejected by the nucleus with the ionospheric ions. Apparently rays are discret structures because the diamagnetic character of the cloudlets that originated the rays. The lengthening of rays was analysed with the objective to investigate the cometary ions movement inside the rays. The slippage of the vertex of rays was interpreted as a result of the transient character of the contact surfaces, since they appear at the moment of intermitent ejection of matter, but, soon after, they shrink themselves and disappear.
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