Low-Frequency Electrostatic Waves in Dusty Plasmas

Details Low-Frequency Electrostatic Waves in Dusty Plasmas Low-Frequency Electrostatic Waves in Dusty Plasmas

Nov 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997phdt.........6b&link_type=abstract

Thesis (PHD). THE UNIVERSITY OF IOWA , Source DAI-B 58/05, p. 2489, Nov 1997, 106 pages.

Computer Science

1

Dust Acoustic Waves, Electrostatic Ion Cyclotron

Scientific paper

Four related types of low-frequency, electrostatic waves (or instabilities) in dusty plasmas are studied experimentally and∨ theoretically. A general dispersion relation, encompassing all four modes, is derived using the fluid equations, and four individual dispersion relations are derived from it. Two of the wave modes, of higher frequency, correspond to the well-known ion acoustic and electrostatic ion cyclotron waves; two brand new, extremely-low frequency modes appear, named the 'dust acoustic wave' and the 'electrostatic dust cyclotron wave,' because the dust motion is analogous to the ion motion in the first two wave modes. For grid-launched ion acoustic waves, the phase velocity increases as the concentration of negatively-charged dust increases. The collisionless (Landau) damping decreases as a result. For the current-driven ion acoustic instability, the frequency of the waves increases as the concentration of negatively-charged dust increases. These results are in agreement with predictions from Vlasov's theory. It was found that dusty plasmas behave in a similar manner to negative ion plasmas, as far as ion acoustic waves are concerned. Electrostatic ion cyclotron (EIC) waves are excited in the conventional manner by drawing an electron current along the magnetic field to a small exciter disk. The amplitude of the waves is larger in the presence of the dust than in the dust-free plasma. The electron drift velocity along the magnetic field needed to excite the waves is smaller in the presence of the dust. One of the earliest observations of the so called dust acoustic wave mode is reported. The extremely-low frequency oscillations in the dust density are found to have a phase velocity similar to that predicted by fluid theory. The waves are found to travel without dispersion over a range of frequencies. The hypothetical 'electrostatic dust cyclotron' wave is briefly considered, to address the feasibility of observing this wave experimentally.

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