Absence of a magnetic-field signature in plasma-wave observations at Callisto

被引:25
作者
Gurnett, DA
Kurth, WS
Roux, A
Bolton, SJ
机构
[1] UNIV VERSAILLES, CTR ETUD ENVIRONM TERR & PLANETAIRES, F-78140 VELIZY VILLACOUBLAY, FRANCE
[2] CALTECH, JET PROP LAB, PASADENA, CA 91109 USA
关键词
D O I
10.1038/387261a0
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
The galilean moons of Jupiter are substantial bodies-three of them are larger than the Earth's Moon, and one is larger than Mercury-yet little has been known about them until very recently. The discovery of a magnetosphere(1) and magnetic field(2) associated with Ganymede was surprising, and raised the possibility that other galilean satellites,. particularly Callisto (which is the second largest after Ganymede), also might have an internally generated magnetic field. Here we report observations of plasma waves around Callisto, detected during the recent fly-by of the Galileo spacecraft. The nature of the plasma waves indicates that Callisto, unlike Ganymede, does not have a magnetosphere or an internal magnetic field The electron density near Callisto, however, is substantially higher than that in Jupiter's magnetosphere at this orbital radius, indicating that Callisto is a significant source of locally generated plasma, This plasma most probably comes from a tenuous atmosphere around Callisto, which may be similar to the hydrogen cloud around Ganymede, as the electron densities are somewhat comparable.
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页码:261 / 262
页数:2
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