Galileo observes electromagnetically coupled dust in the Jovian magnetosphere

Measurements of dust coupled to the Jovian magnetosphere have been obtained with the dust detector on board the Galileo spacecraft. We report on data obtained during the first four orbits about Jupiter that had flybys of the Galilean satellites: Ganymede (orbits 1 and 2), Callisto (orbit 3), and Europa (orbit 4). The most prominent features observed are highly time variable dust streams recorded throughout the Jovian system. The impact rate varied by up to 2 orders of magnitude with a 5 and 10 hour periodicity, which shows a correlation with Galileo's position relative to the Jovian magnetic field. Around 20 RJ (Jupiter radius, RJ=71, 492 km) in bound a dip in the impact rate has been found consistently. At the same times, reversals by 180° in impact direction occurred. This behavior can be qualitatively explained by strong coupling of nanometer-sized dust to the Jovian magnetic field. At times of satellite flybys, enhanced rates of dust impacts have been observed, which suggests that all Galilean satellites are sources of ejecta particles. Inside about 20 RJ impacts of micrometer-sized particles have been recorded that could be particles on bound orbits about Jupiter. (Less)

[1]  David P. Hamilton,et al.  Dust Measurements During Galileo's Approach to Jupiter and Io Encounter , 1996, Science.

[2]  E. Grün,et al.  The Galileo Dust Detector , 1992 .

[3]  S. Collins.  Spatial color variations in the volcanic plume at Loki, on Io , 1981 .

[4]  E. Grün,et al.  Ulysses dust measurements near Jupiter. , 1992, Science.

[5]  E. Grün,et al.  Mechanism for the acceleration and ejection of dust grains from Jupiter's magnetosphere , 1993, Nature.

[6]  J. Burns,et al.  Discovery of Jupiter's ‘gossamer’ ring , 1985, Nature.

[7]  David P. Hamilton,et al.  Solar Wind Magnetic Field Bending of Jovian Dust Trajectories , 1996, Science.

[8]  M. Kivelson,et al.  Constraints from Galileo observations on the origin of jovian dust streams , 1996, Nature.

[9]  H. Fechtig,et al.  Discovery of Jovian dust streams and interstellar grains by the Ulysses spacecraft , 1993, Nature.

[10]  R. Probstein,et al.  A theory of dust comets. I. Model and equations , 1968 .

[11]  Eberhard Grün,et al.  Identification of “small” dust impacts in the Ulysses dust detector data , 1993 .

[12]  E. Grün,et al.  Modeling the Galileo dust measurements at Jupiter , 1997 .

[13]  R. Probstein,et al.  A THEORY OF DUST COMETS , 1967 .

[14]  R. Srama,et al.  Dust measurements in the Jovian magnetosphere , 1997 .

[15]  J. Burns,et al.  Ejection of dust from Jupiter's gossamer ring , 1993, Nature.

[16]  D. H. Humes,et al.  Results of Pioneer 10 and 11 Meteoroid Experiments: Interplanetary and near‐Saturn , 1980 .

[17]  E. Grün,et al.  Jupiter's exogenic dust ring , 1998 .

[18]  E. Grün,et al.  The dusty ballerina skirt of Jupiter , 1993 .

[19]  D. H. Humes,et al.  The interplanetary and near‐Jupiter meteoroid environments , 1974 .

[20]  E. Grün,et al.  Reduction of Galileo and Ulysses dust data , 1995 .