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キーワード:
Jovian dust streams, frequency analysis, Cassini-Galileo dust measurements, Io's volcanoes.
要旨:
The Jovian dust streams are high-speed bursts of submicron-sized particles traveling in the same direction from a source in the Jovian system. Since their discovery in 1992, they have been observed by three spacecraft: Ulysses, Galileo and Cassini. The source of the Jovian dust streams is dust from Io's volcanoes. The charged and traveling dust stream particles have particular signatures in frequency space and in real space. The frequency-transformed Galileo dust stream measurements show different signatures, varying orbit-to-orbit during Galileo's first 29 orbits around Jupiter. Time-frequency analysis demonstrates that Io is a localized source of charged dust particles. Aspects of the particles' dynamics can be seen in the December 2000 joint Galileo-Cassini dukst stream measurements. To match the travel times, the smallest dust particles could have the following range of parameters: radius: 6 nm, density: 1.35-1.75 g/cm3, sulfur charging conditions, which produce dust stream speeds: 220\450 km s-1 (Galileo\Cassini) and charge potentials: 5.5\6.3 V (Galileo\Cassini).
