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Cravens 1997
Cravens, T.E. (1997). Comet Hyakutake x-ray source: Charge transfer of solar wind heavy ions. Geophysical Research Letters 24: doi: 10.1029/96GL03780. issn: 0094-8276.

Recently, Lisse et al. (1996) reported on exciting observations by the R¿ntgen X-ray satellite (ROSAT) of x-ray and extreme ultraviolet emissions from comet C/Hyakutake 1996 B. The spatial distribution of the emissions was displaced sunward of the nucleus and the spatial extent was about 105km. Lisse et al (1996) suggested that the emission could be explained by thermal bremsstrahlung associated with hot electrons, possibly due to solar wind interaction effects. In the present paer, an alternate emission mechanism is proposed. The solar wind contains a large number of minor/heavy ion species with a range of charge states, such as O6+, C5+, N5+, Si10+. These ions will readily charge transfer with cometary neutrals, producing ions which can be highly excited and consequently emit photons in the extreme ultraviolet and x-ray part of the spectrum. The photon emission rate is proportional to the solar wind heavy ion flux and hence to the solar wind flux and, with some assumptions concerning the solar wind velocity, to the solar wind velocity, to the solar wind number density. The emission rate should be greatest downstream of the bow shock along the sun-comet axis in agreement with the observed spatial distribution. The x-ray images are really images of the line of sight integration of the solar wind density convoluted with the cometary neutral density. A total EUV/x-ray luminosity for comet Hyakutake from this charge transfer mechanism agrees with the observed luminosity of 4¿1015 ergs s-1 within a factor of two.¿American Geophysical Union

BACKGROUND DATA FILES

Abstract

Keywords
Planetology, Comets and Small Bodies, Interactions with solar wind plasma and fields, Planetology, Comets and Small Bodies, Radiation and spectra, Interplanetary Physics, Solar wind plasma
Journal
Geophysical Research Letters
http://www.agu.org/journals/gl/
Publisher
American Geophysical Union
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