Dynamics of Rayleigh-Taylor Instability in Plasma Fluids

The chapter discusses the evolution of Rayleigh-Taylor instability (RTI) in ordinary fluids and in a plasma fluid. RT instability exits in many situations from overturn of the outer portion of the collapsed core of a massive star to laser implosion of deuterium-tritium fusion targets. In the mixture of fluids, the instability is triggered by the gravitational force acting on an inverted density gradient. The motivation behind the study of the instability has been explored by discussing the applications of RT instability. The basic magnetohydrodynamics equations are used to derive the dispersion relation (for an ordinary fluid and plasmas) for two fluids of unequal densities. The conditions of the growth rate of the instability and the propagating modes are obtained by linearizing the fluid equations. The perturbed potential is found to increase with the plasma parameters in a Hall thruster

Waves and Instabilities in E × B Dusty Plasma

Hall thrusters are common examples of E × B configuration, where electron trajectory gets trapped along the external magnetic field lines. This significantly increases the residence time of electrons in the plasma discharge channel. Hall thrusters are potential candidates for spacecraft station keeping, rephrasing and orbit topping applications because of its high thrust resolutions and efficiency. The goal of this chapter is to explain the working principle of Hall thrusters and to characterize the resistive instability in hot dusty plasma. The studies of these instabilities are useful to design efficient Hall thrusters and to understand the solar dusty plasma. The large amplitude of these oscillations has an adverse effect on the power processing unit of the devices. This reduces the efficiency and specific impulse and shortens the operating life of the Hall thruster. The theory of linearization of fluid equation for small oscillation has been given. The chapter also discusses the origin of plasma oscillation in a plasma discharge mechanics

Shear Strength Characteristics of Heavily Glaciated Soils of Chugach Range

As a part of the evaluation of the stability of cut slope of 55% grade, during the construction of Trans-Alaska pipeline, it was realized that the estimation of the strength characteristics of the glaciated till forming the slopes is vital to the analysis and the design of these slopes. Accordingly undisturbed samples were hand carved from block samples and were tested fro shear strength. An usually high effective angles of friction, 45° - 48° (Singh, 1976) were obtained. However, these high values of friction were found to be inconsistent with the maximum angle which the cut slopes can withstand. The paper presents the results of tests and analysis and explains the unusual behavior and bring into focus the special considerations required in extending methodology of temperate regions to slopes of cold regions

Hall Thruster: An Electric Propulsion through Plasmas

The chapter discussed the technological application of plasma physics in space science. The plasma technology is using laser-plasma fusion, inertial fusion, Terahertz wave generation and welding of metals. In this chapter, the application of plasma physics in the field of electric propulsion and types has been discussed. These devices have much higher exhaust velocities, longer life time, high thrust density than chemical propulsion devices and useful for space missions with regard to the spacecraft station keeping, rephrasing and orbit topping applications. The mathematical relation has been derived to obtain the performance parameters of the propulsion devices

Performance of Concrete Faced Earthdam to Loma Prieta Earthquake

As a result of the shaking from the Loma Prieta Earthquake of 1989, the concrete lining of an earth embankment suffered cracking at numerous locations on its upstream side and developed in its bed lining, crater-like pot-holes ranging in size up to 10 ft. in diameter. Field investigation and preliminary studies indicated the differential dynamic vibrations of the earth embankment and the concrete lining to be the cause of the cracking, and the liquefaction of the underlying stratum below the bottom of the reservoir to be the cause of the pot-holes formed as a result of the pore pressure bursting through cracks in the lining. This paper presents a summary of the investigation and the related studies

Evolutions of Growing Waves in Complex Plasma Medium

The purpose of this chapter to discuss the waves and turbulence (instabilities) supported by dusty plasma. Plasmas support many growing modes and instabilities. Wave phenomena are important in heating plasmas, instabilities, diagnostics, etc. Waves in dusty plasma are governed by the dynamics of electrons, ions and dust particles. Disturbances in solar wind, shocks and magnetospheres are the sources of generation of plasma waves. The strong interest in complex plasma provides us better understanding of physics of dusty universe, solar winds, shocks, magnetospheres, dust control in plasma processing units and surface modifications of materials. The theory of linearization of fluid equation for small oscillation has been introduced. The concept of fine particles in complex plasma and its importance is also explained. The expressions for the growth rate of the instabilities in turbulence plasma have been derived

Physics of Absorption and Generation of Electromagnetic Radiation

The chapter is divided into two parts. In the first part, the chapter discusses the theory of propagation of electromagnetic waves in different media with the help of Maxwell’s equations of electromagnetic fields. The electromagnetic waves with low frequency are suitable for the communication in sea water and are illustrated with numerical examples. The underwater communication have been used for the oil (gas) field monitoring, underwater vehicles, coastline protection, oceanographic data collection, etc. The mathematical expression of penetration depth of electromagnetic waves is derived. The significance of penetration depth (skin depth) and loss angle are clarified with numerical examples. The interaction of electromagnetic waves with human tissue is also discussed. When an electric field is applied to a dielectric, the material takes a finite amount of time to polarize. The imaginary part of the permittivity is corresponds to the absorption length of radiation inside biological tissue. In the second part of the chapter, it has been shown that a high frequency wave can be generated through plasma under the presence of electron beam. The electron beam affects the oscillations of plasma and triggers the instability called as electron beam instability. In this section, we use magnetohydrodynamics theory to obtain the modified dispersion relation under the presence of electron beam with the help of the Poisson’s equation. The high frequency instability in plasma grow with the magnetic field, wave length, collision frequency and the beam density. The growth rate linearly increases with collision frequency of electrons but it is decreases with the drift velocity of electrons. The real frequency of the instability increases with magnetic field, azimuthal wave number and beam density. The real frequency is almost independent with the collision frequency of the electrons

Numerical Investigations of Electromagnetic Oscillations and Turbulences in Hall Thrusters Using Two Fluid Approach

The first part of the contributed chapter discuss the overview of electric propulsion technology and its requirement in different space missions. The technical terms specific impulse and thrust are explained with their relation to exhaust velocity. The shortcoming of the Hall thrusters and its erosion problems of the channel walls are also conveyed. The second part of the chapter discuss the various waves and electromagnetic instabilities propagating in a Hall thruster magnetized plasma. The dispersion relation for the azimuthal growing waves is derived analytically with the help of magnetohydrodynamics theory. It is depicted that the growth rate of the instability increases with magnetic field, electron drift velocity and collisional frequency, whereas it is decreases with the initial drift of the ions