Study On The Electrostatic Waves In The Dusty Plasmas

In recent 20 years, particularly in the recent decade, dusty plasmas have been extensively studied. The study on electrostatic dusty plasma waves is a fundamental area in dusty plasma researches. The characteristics of the plasmas can be obtained in the wave studies. Furthermore, the electrostatic waves can help the stability analysis of the system. Laboratory observations of dusty plasma crystals have opened a new research area in dusty plasma physics. A dusty plasma crystal is a strongly coupled system. It is then a perfect model for studying phase transition and important properties of solid state matters in a macroscopic level, due to that fact that it can be controlled conveniently and observed easily and macroscopically in experiments. Lattice waves in the dusty plasma crystals are typical electrostatic modes. Many key plasma parameters can be obtained in studying on the electrostatic dusty plasma waves. Therefore the electrostatic wave study has become a very important diagnostic method for dusty plasmas.The electrostatic waves in dusty plasmas have been systematically studied in this thesis.In the first chapter, a brief review of dusty plasmas has been made, including the basic concepts of dusty plasma physics, its existence and general study methods. And then, the basic introduction of the dusty plasma waves is given.In the second chapter, by using the multi-fluid hydrodynamic equations, the electrostatic waves of the dusty plasma in a uniform magnetic field are investigated. In the usual experimental condition, the dust particles are hardly magnetized due to the small radio of its charge to mass, while the electrons and ions are easily done so. The "moderately magnetized" dusty plasma is then proposed, i.e. the electrons and ions are magnetized and the dust particles are unmagnetized. The general dispersion relations are derived and discussed in different frequency ranges. Besides the well known electrostatic modes, a new very low frequency mode is found.In the chapter three, based on the second chapter, by considering the damping effect of the neutral gas and the ion drag force on the dust particle, the electrostatic modes and their instabilities in the dusty plasma in the uniform magnetic field are investigated. It is shown that the waves in the medium and low frequency range are damped.In the chapter four, effects of the dust finite size on the lattice waves in the one-dimensional dust chain are investigated. Dust particles are usually levitated in the sheath region above the electrode where the gravity is balanced by the vertical electric field force. And thesupersonic ion flow is induced by the electric field in the sheath region. In this situation, the charge distribution on the particle's surface is inhomogeneous. This can be embodied by assuming each dust particle to be a negative point charge plus a dipole moment charge. The dispersion relations of the longitudinal and transverse waves are derived and discussed when they are self-excited and externally excited respectively. It is shown that the lattice waves are significantly affected by the dipole moment and sensitive to the direction of the dipole moment.In the chapter five, the anisotropy of the vertical transverse wave in the two-dimensional monolayer is investigated. Also the effects of the dipole moment on the vertical transverse wave are discussed. The result is similar to the horizontal transverse wave in one-dimensional dust chain discussed in chapter three. This is because that both of them are confined in the direction of the particle's motion.In the chapter six, the effects of wake potential on the lattice waves are investigated. Introducing the effective point charge of the wake potential can greatly simplify the problem we discussed. By comparing the dispersion relations with the experimental data, we find that the existing well-known positive equivalent charge model is invalid. After the detailed analysis of the net charge downstream of the particle, we find that the equivalent charge should be negative. The dispersion relations derived by using our new model are in a good agreement with the experimental data.At last, a brief summary is given to end the thesis.