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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1961

Experiments with Plasmas Produced by Potassium-Seeded Cyanogen Oxygen Flames for Study of Radio Transmission at Simulated Reentry Vehicle Plasma Conditions

A method for the chemical production of an ionized gas stream for application to radio transmission studies is described. Involved is the combustion of gaseous cyanogen and oxygen with the addition of vaporized potassium in some cases to further increase the ionization. Experiments are described in which a 3-inch-diameter subsonic free jet at atmospheric pressure is used, and the results are presented. The plasma obtained by using this method is sufficient to simulate plasma conditions expected for reentering hypersonic vehicles. The unseeded plasma stream temperature is indicated to be about 4,200 K, with the degree of ionization indicated to be that expected from thermal equilibrium considerations. Measurements of radio-signal loss due to the unseeded flame plasma are presented for microwaves of 8 to 20 kmc transmitted through the stream and for a dipole transmitting model of 219.5 mc immersed in the stream. Favorable comparison of these results with the simple plane-wave signal-attenuation theory was obtained. In the case of a 9.4-kmc microwave signal of 30-kw peak power, the preliminary indication is that the plasma characteristics were not changed due to this strong signal. Comparison of a simplified concept of radio-signal attenuation due to plasmas is made with some hypersonic reentry vehicle signal-loss data. Other areas of plasma research using this method for the transmission problem are indicated.

Huber, Paul W.↗
DOE OSTI2024

Higher-form symmetry and chiral transport in real-time Abelian lattice gauge theory

We study classical lattice simulations of theories of electrodynamics coupled to charged matter at finite temperature, interpreting them using the higher-form symmetry formulation of magnetohydrodynamics (MHD). We compute transport coefficients using classical Kubo formulas on the lattice and show that the properties of the simulated plasma are in complete agreement with the predictions from effective field theories. In particular, the higher-form formulation allows us to understand from hydrodynamic considerations the relaxation rate of axial charge in the chiral plasma observed in previous simulations. A key point is that the resistivity of the plasma – defined in terms of Kubo formulas for the electric field in the 1-form formulation of MHD – remains a well-defined and predictive quantity at strong electromagnetic coupling. However, the Kubo formulas used to define the conventional conductivity vanish at low frequencies due to electrodynamic fluctuations, and thus the concept of the conductivity of a gauged electric current must be interpreted with care.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1983

Numerical simulations of plasma double layers

The results of analytical studies of quasi-static electric fields along geomagnetic field lines are discussed. The calculations were targeted at the structure, generation mechanisms and stability parameters. The field consists of two oppositely charged layers, either weakly or strongly charged, with an electric field between. Existence conditions are defined for the double layer field and balancing requirements are explored. Details of the simulation techniques, i.e., particle in cell and Vlasov simulations, for studying the double layer are outlined, noting that both periodic and quasi-periodic simulations are used. Solutions to Poisson's equation for fixed and floating point boundary conditions are generated. Finally, attention is also given to oblique and two-dimensional magnetic double layers.

Goertz, C. K.↗
NASA NTRS1988

Simulations of plasma structure evolution in the high-latitude ionosphere

The Naval Research Laboratory has recently developed a two-dimensional inertial, electrostatic code which has been successfully applied to the development and evolution of ionospheric structure driven by plasma instabilities. This code models the ionosphere and magnetosphere as a set of horizontal two-dimensional layers which are coupled by the vertical magnetic field lines at high latitudes. It is shown that the development of instability-generated structure can be strongly dependent on this coupling. For example, the influence of magnetospheric coupling on the E x B gradient drift instability is to retard the instability's growth and to isotropize density irregularities. The influence of ionospheric coupling on the Kelvin-Helmholtz instability is to retard its growth and to suppress vortex formation. This paper presents the results of numerical simulations of these instabilities and discusses their application to high-latitude ionospheric structure.

Huba, J. D.↗
NASA NTRS1995

Nonlinear Landau damping and Alfven wave dissipation

Nonlinear Landau damping has been often suggested to be the cause of the dissipation of Alfven waves in the solar wind as well as the mechanism for ion heating and selective preacceleration in solar flares. We discuss the viability of these processes in light of our theoretical and numerical results. We present one-dimensional hybrid plasma simulations of the nonlinear Landau damping of parallel Alfven waves. In this scenario, two Alfven waves nonresonantly combine to create second-order magnetic field pressure gradients, which then drive density fluctuations, which in turn drive a second-order longitudinal electric field. Under certain conditions, this electric field strongly interacts with the ambient ions via the Landau resonance which leads to a rapid dissipation of the Alfven wave energy. While there is a net flux of energy from the waves to the ions, one of the Alfven waves will grow if both have the same polarization. We compare damping and growth rates from plasma simulations with those predicted by Lee and Volk (1973), and also discuss the evolution of the ambient ion distribution. We then consider this nonlinear interaction in the presence of a spectrum of Alfven waves, and discuss the spectrum's influence on the growth or damping of a single wave. We also discuss the implications for wave dissipation and ion heating in the solar wind.

Vinas, Adolfo F.↗
NASA NTRS1977

Computer simulation of plasma and N-body problems

Any spiral structure in computer-generated galaxies is generally short lived and the final state is a rotating bar. The bar thus obtained rotates more slowly than the stars. It has been argued that core/halo components have a stabilizing effect on galaxies and result in longer lived spiral structure. However, numerical experiments with large fixed stellar components representing the core/halo component show that multiarmed spiral structure develops and persists for many rotations but only in an evolving manner. That is, the spiral structure is either wound up into a tight pattern or it is wound up and then reappears again. A recent study of the effect of fixed core/halo components does show that the bar instability is indeed inhibited by a sufficiently large fixed component. The present study determines the effect of a self-consistent (rather than fixed) core/halo component in order to show whether there are any instabilities (such as two-stream) or other important interactions present that may be suppressed with a fixed core. Also studied were the effects of finite thickness of the disk and of three-dimensional essentially spherical core/halo components.

Harries, W. L.↗
NASA NTRS1985

Computer simulation of plasma electron collection by PIX-II

A wake model was defined for the NASCAP/LEO finite element model for the plasma interaction experiment (PIX-II) launched to study the interaction between high-voltage large solar arrays with the space plasma environment. The cell surface model considers the individual cells, distances between interconnects, and the fraction of surface covered by interconnects. Account is taken of the electrostatic potential around the spacecraft, which travels at 7500 mps, over five times the speed of thermal ions. Ram ions are produced ahead of the array and the wake ion density is described with a geometric shadowing model. The model correctly predicted the currents in high and low bias voltages when compared to orbital data. The panel snapover, however, was projected to occur at 100 V and instead occurred at 300 V, which indicates that the snapover state is bistable. Finally, a low potential was both predicted and measured in the wake.

Mandell, M. J.↗
NASA NTRS1990

Plasma particle simulation of electrostatic ion thrusters

Charge exchange collisons between beam ions and neutral propellant gas can result in erosion of the accelerator grid surfaces of an ion engine. A particle in cell (PIC) is developed along with a Monte Carlo method to simulate the ion dynamics and charge exchange processes in the grid region of an ion thruster. The simulation is two-dimensional axisymmetric and uses three velocity components (2d3v) to investigate the influence of charge exchange collisions on the ion sputtering of the accelerator grid surfaces. An example calculation has been performed for an ion thruster operated on xenon propellant. The simulation shows that the greatest sputtering occurs on the downstream surface of the grid, but some sputtering can also occur on the upstream surface as well as on the interior of the grid aperture.

Peng, Xiaohang↗