ELECTRON TEMPERATURES IN THE UPPER ATMOSPHERE
Energy loss processes for fast electrons, electron heating efficiency, heat input to the electron gas, effect of thermal coupling, and electron thermal conductivity above the f2 peak
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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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Numerical investigation of fluid models with full electron and proton thermal conduction equations for the quiet solar wind
The effect of using full equations (rather than Fourier law expressions) for the electron and proton thermal conductivities in conjunction with community, momentum, and temperature equations for the description of spherically symmetric quiet solar wind states is investigated numerically. For this purpose a time-dependent method is used, and steady state solutions in both subsonic and supersonic regimes between the sun and 5 AU are obtained and presented. The consequences for one-fluid and two-fluid models for the solar wind are summarized and discussed.
Cuperman, S.↗
Effects of interhemisphere transport on plasma temperatures at low latitudes.
The thermal balance of the equatorial plasma between 300 and 800 km is examined. Steady state nighttime calculations are made for O+, H+, and electrons. The following features are included: collisional heat transfer between ions, electrons, and neutrals; ion and electron thermal conduction along the field lines; curvature of the field lines; nonlinear advection due to field-aligned ion and electron motions; and convective compression or expansion due to field-aligned and E x B motions. The ion velocities necessary to calculate the effects of convection are obtained from the work of Moffett and Hanson, who include a meridional wind across the magnetic equator in their calculations. It is shown that field-aligned interhemisphere plasma flows appreciably affect the plasma temperatures.
Bailey, G. J.↗
Effect of anomalous transport coefficients on the thermal structure of the storm time auroral ionosphere
By analyzing an observed storm time auroral electron temperature profile it is shown that anomalous transport effects strongly influence the thermal structure of the disturbed auroral ionosphere. Such anomalous transport effects are a consequence of plasma turbulence, the existence of which has been established by a large number of observations in the auroral ionosphere. The electron and composite ion energy equations are solved with anomalous electron thermal conductivity and parallel electrical resistivity coefficients. The solutions are parameterized with respect to a phenomenological altitude-dependent anomaly coefficient A and are compared with an observed storm time electron temperature profile above Chatanika. The calculated temperature profile for the classical case (A = 1) disagrees considerably with the measured profile over most of the altitude range up to 450 km. It is shown that an anomaly coefficient with a sharp peak of the order of 10,000 centered around the F2 peak is consistent with observations.
Fontheim, E. G.↗
Another self-similar blast wave: Early time asymptote with shock heated electrons and high thermal conductivity
Accurate approximations are presented for the self-similar structures of nonradiating blast waves with adiabatic ions, isothermal electrons, and equation ion and electron temperatures at the shock. The cases considered evolve in cavities with power law ambient densities (including the uniform density case) and have negligible external pressure. The results provide the early time asymptote for systems with shock heating of electrons and strong thermal conduction. In addition, they provide analytical results against which two fluid numerical hydrodynamic codes can be checked.
Cox, D. P.↗
Joining Carbon-Carbon Composites and High-Temperature Materials with High Energy Electron Beams
1. Program goals addressed during this period. Experimental work was directed at formation of a low-stress bond between carbon- carbon and aluminum, with the objective of minimizing the heating of the aluminum substrate, thereby minimizing stresses resulting from the coefficient of thermal expansion (CTE) difference between the aluminum and carbon-carbon. A second objective was to form a bond between carbon-carbon and aluminum with good thermal conductivity for electronic thermal management (SEM-E) application. 2. Substrates and joining materials selected during this period. Carbon-Carbon Composite (CCC) to Aluminum. CCC (Cu coated) to Aluminum. Soldering compounds based on Sn/Pb and Sn/Ag/Cu/Bi compositions. 3. Soldering experiments performed. Conventional techniques. High Energy Electron Beam (HEEB) process.
Goodman, Daniel↗
Analysis of the diffusion-dominated thermionic converter plasma.
J-V characteristics of diffusion dominated cesium thermionic converter plasma, describing electron thermal conductivity and volume ionization effects
Bornhorst, W.↗
Fully ionized quasi-one dimensional magnetic nozzle flow
Fully ionized quasi-one dimensional magnetic nozzle flow analysis, including effects of unequal electron and ion temperatures and electron thermal conductivity
Chubb, D. L.↗
Propagation of hydromagnetic waves in the upper F2-region
The theory of hydromagnetic-wave in the upper F2-region, in which electrons are in a transitional regime from collisional to collisionless conditions and ions are in a collisionless state, is examined. Derivation of the governing equations is based on the fact that the isotropic electrons are fluid-like, and the anisotropic ions follow kinetic equations modified by ion-electron collisions. Magneto-acoustic waves of a period of from about 0.2 to 10 sec are dissipated by ion Landau damping and electron thermal conduction and viscosity. Numerical solutions under ionospheric conditions show that the dissipation of hydromagnetic waves is insufficient to modify the large scale heating of the ionosphere.
Hung, R. J.↗
Observational evidence for thermal wave fronts in solar flares
Images in 3.5-30 keV X-rays obtained during the first few minutes of seven solar flares show rapid motions. In each case X-ray emission first appeared at one end of a magnetic field structure, and then propagated along the field at a velocity between 800 and 1700 km/s. The observed X-ray structures were 45,000-230,000 km long. Simultaneous H-alpha images were available in three cases; they showed brightenings when the fast-moving fronts arrived at the chromosphere. The fast-moving fronts are interpreted as electron thermal conduction fronts since their velocities are consistent with conduction at the observed temperatures of 1-3 x 10 to the 7th K. The inferred conductive heat flux of up to 10-billion ergs/s sq cm accounts for most of the energy released in the flares, implying that the flares were primarily thermal phenomena.
Rust, D. M.↗
Radiative shock oscillations in AM Her cataclysmic binaries
The stability properties of radiative shocks in spherically symmetric accretion flows onto white dwarfs is discussed. Accretion rates that result in shock thicknesses ranging from thin to settling solutions are investigated. Models for white dwarf masses from 0.3 to 1.2 of the solar mass are presented. The effects of unequal ion and electron temperatures, electron thermal conduction, bremsstrahlung, and Compton cooling are included. It is shown that thick two-temperature shocks are unstable to oscillations in the fundamental mode for white dwarf mass up to and including 1.0 of the solar mass. The possibility that the 0.3 to 1.0 Hz optical Quasi-Periodic Oscillations (QPOs) observed in four AM Her type cataclysmic binaries are due to the first overtone instability. Low accretion rate shock instabilities may be responsible for the tens of seconds to several minute X-ray QPOs observed in some AM Her objects.
Wolff, M. T.↗
Emission processes and dynamics of hot gases in astrophysics
A detailed model was developed for Kepler's supernova remnant (SNR). Observations of the SNR revealed a strong interaction with the surrounding circumstellar medium, which was studied through both analytical and numerical calculations. Effects were studied of electron thermal conduction on the structure of radiative interstellar shock waves. An explanation is sought for the observed line emission from metal rich ejecta in SNR, incorporating atomic data. Light echoes around SN 1987A was also studied. Analysis of infrared and scattered circumstellar light echoes was accomplished with early observations to set limits on the mass of circumstellar dust. Work was completed on the emission from heavy element gas ejected in the supernova explosion of massive stars. It was assumed that a radioactive energy source was present and calculated the detailed heating and ionization of the gas. The evolution was studied of SNR in the very high pressure environment of a starburst galaxy.
Chevalier, Roger A.↗
Another self-similar blast wave - Early time asymptote with shock-heated electrons and high thermal conductivity
(Previously announced in STAR as N82-19962)
Cox, D. P.↗
Thermal conduction and heating by nonthermal electrons in the X-ray halo of M87
A hydrostatic model for the X-ray halo around the giant elliptical galaxy M87 is presented. It is shown that by taking into account the processes of thermal conduction, and nonthermal heating by relativistic electrons in the radio lobes, a self-consistent hydrostatic model can be constructed. There is no need to invoke radiative accretion or the suppression of thermal conductivity.
Tucker, W. H.↗
Thermal Conductivity and Temperature Limits of Electron-Beam Physical-Vapor-Deposited ZrO2-7wt%Y2O3 Thermal Barrier Coating
The electron-beam physical-vapor-deposited (EB-PVD) ZrO2-7wt%Y2O3 thermal barrier coating has been widely used to protect engine hot section components in modem aircraft engines. Thermal conductivity and the conductivity increases due to sintering and phase changes are important coating design parameters. There is a need to characterize the coating thermal conductivity behavior and temperature limits, in order to potentially take full advantage of the coating capability. In addition, since the ZrO2-7wt%Y2O3 coating is often used as a baseline coating for the development of advanced lower thermal conductivity and higher temperature capability coatings, a thorough evaluation of the coating conductivity behavior at future higher engine operating temperatures will be useful for more accurately assessing the benefit gained from the new coating systems. In this study, thermal conductivity behavior of EB-PVD ZrO2-7wt%Y2O3 coating has been systematically investigated as a function of temperature (up to 2600 F) and time under steady-state and cyclic test conditions using a laser heat-flux technique. Thermal conductivity change kinetics were determined under realistic engine high temperature thermal gradient conditions, and correlated to the coating microstructural and phase changes. The thermal conductivity prediction models have been established in terms of heat flux, time, and testing temperatures.
Zhu, Dongming↗
Thermal Conductivity of EB-PVD Thermal Barrier Coatings Evaluated by a Steady-State Laser Heat Flux Technique
The thermal conductivity of electron beam-physical vapor deposited (EB-PVD) Zr02-8wt%Y2O3 thermal barrier coatings was determined by a steady-state heat flux laser technique. Thermal conductivity change kinetics of the EB-PVD ceramic coatings were also obtained in real time, at high temperatures, under the laser high heat flux, long term test conditions. The thermal conductivity increase due to micro-pore sintering and the decrease due to coating micro-delaminations in the EB-PVD coatings were evaluated for grooved and non-grooved EB-PVD coating systems under isothermal and thermal cycling conditions. The coating failure modes under the high heat flux test conditions were also investigated. The test technique provides a viable means for obtaining coating thermal conductivity data for use in design, development, and life prediction for engine applications.
Zhu, Dongming↗
On the thermal conductivity due to collisions between relativistic degenerate electrons
A numerical integration is undertaken of the integral expression for the thermal conductivity due to collisions of relativistic degenerate electrons and compared to the limiting-case analytic formula. The integration is designed to encompass all temperature/electron-plasma-frequency temperature ratios between the melting temperature and the Fermi temperature. High accuracy fits are demonstrated by interpolating the values of the integrals of the function and by using an asymptotic function by Urpin and Yakovlev (1980). The numerically integrated expression compares favorably to the limiting-case analytic asymptotic formula by Urpin and Yakovlev, and the results are valid for temperatures above and below the electron-plasma-frequency temperature. The present techniques can be used in stellar opacity calculations and in the study of the propagation of deflagration fronts of compact stellar remnants.
Timmes, F. X.↗
Some physical implications of recent solar wind measurements
The physical implications of the existence at about 1 AU of a quiet solar wind particle flux about 90 percent larger than that suggested in the past is investigated within the framework of the two-fluid solar wind model equations. During the spherically symmetric radial expansion of the quiet solar wind, the particle flux is conserved quantity. It is found that a pure collisional two-fluid model provides good particle density and streaming velocity at 1 AU, but predicts too large an electron temperature and too small a proton temperature. When noncollisional contributions to the transport coefficients are incorporated in the model equations, a complete satisfactory agreement with the available observations is obtained. Upper limits to the effective coupling between electrons and protons, as well as to the effective proton thermal conductivity, and both upper and lower limits to the effective electron thermal conductivity in the quiet solar wind, required to provide agreement with observations, are given.
Cuperman, S.↗