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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 100, NO. A2, PAGES 1731–1734, 1995

Probing the Properties of Planetary Ring Dust by the Observation of Mach Cones

O. Havnes

Auroral Observatory, University of Tromsø, Tromsø, Norway.


T. Aslaksen

Auroral Observatory, University of Tromsø, Tromsø, Norway.


T. W. Hartquist

Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany.


F. Li

Auroral Observatory, University of Tromsø, Tromsø, Norway.


F. Melandsø

Auroral Observatory, University of Tromsø, Tromsø, Norway.


G. E. Morfill

Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany.


T. Nitter

Auroral Observatory, University of Tromsø, Tromsø, Norway.


Abstract

Compressive dust acoustic waves can be excited in dusty plasmas. Big boulders in planetary rings move at the Keplerian velocity, while smaller dust particles move at a slightly different velocity due to the action of the Lorentz force. If the difference in velocity Δυ is larger than the dust acoustic wave velocity, α d , a wake will be formed with an opening angle of 2θ where sin θ = |α d /Δυ|. The discovery of wakes and the measurement of their opening angles by the space experiment Cassini to Saturn will yield added information on the dusty plasma conditions in regions through which Cassini will not pass. We find that in some regions the waves that are excited by the boulders may be weak because a large fraction of the interacting dust is absorbed rather than deflected by the boulder. For a given dust size the most favourable conditions for the observations of wakes exist in two fairly narrow regions, one inside and one outside the corotation radius. The favorable regions are closest to the corotation radius for the smallest dust particles and progressively further away for larger dust particles.

Received 4 January 1994; accepted 13 October 1994.

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Citation: Havnes, O., T. Aslaksen, T. W. Hartquist, F. Li, F. Melandsø, G. E. Morfill, and T. Nitter (1995), Probing the Properties of Planetary Ring Dust by the Observation of Mach Cones, J. Geophys. Res., 100(A2), 1731–1734.