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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 NTRS1984

Egress spectra of the new eclipsing supergiant 22 Vulpeculae

The G-type primary in the single-lined spectroscopic binary 22 Vul (HD 192713, Gp3 Ib-II, period 249 days) was found by IUE to eclipse its recently identified B9 main sequence companion. The system thus joins Zeta Aurigae systems in which a hot dwarf provides a probe of extended atmospheres by going behind a cool supergiant. The IUE data were obtained at scattered dates following two conjunctions. Outside of eclipse, a wind from the system with terminal velocity of 300 k/sec is conspicuous in the Mg II lines. Enhanced Fe II absorption seen well away from geometrical eclipse implies an extensive envelope around the G star. There is a close correspondence between the 22 Vul spectra and those of interacting binaries, suggesting common properties due to relatively dense, warm plasmas in these systems.

Ake, T. B., III↗
NASA NTRS1984

The ion cyclotron dispersion relation in a proton-alpha solar wind

Solutions to the WKB warm plasma dispersion relation are investigated for the case of a proton-alpha plasma, to determine when parallel ion cyclotron waves can propagate at the alpha particle gyrofrequency. Examples are given of the behavior of the dispersion curves in this resonant regime, for several types of plasma states that are appropriate to the fast solar wind. It is found that while ion cyclotron waves can propagate at the alpha particle gyrofrequency for a bounded set of plasma parameters, use of the correct dispersion relation will probably make resonant cyclotron acceleration of solar wind plasma particles less feasible as a mechanism for the generation of the observed preferential effects.

Isenberg, P. A.↗
NASA NTRS1987

The onset of Alfvenic turbulence

An investigation is conducted on how low-frequency MHD oscillations in a warm plasma may undergo a transition from a coherent state to one of turbulence. A driven/dissipative derivative nonlinear Schroedinger equation is derived from the fluid equations. The time evolution of an arbitrary spectrum of waves is analyzed in the case where one k-mode is unstable, with the rest damped. It is found that the transition from order to chaos in the driven/dissipative system is correlated with the existence or absence of 'breathing' solitons in the associated conservative system.

Ghosh, S.↗
NASA NTRS1989

The theory of magnetohydrodynamic wave generation by localized sources. II - Collisionless dissipation of wave packets

The dispersion equation of Barnes (1966) is used to study the dissipation of asymptotic wave packets generated by localized periodic sources. The solutions of the equation are linear waves, damped by Landau and transit-time processes, in a collisionless warm plasma. For the case of an ideal MHD system, most of the waves emitted from a source are shown to cancel asympotically through destructive interference. The modes transporting significant flux to asymptotic distances are found to be Alfven waves and fast waves with theta (the angle between the magnetic field and the characteristics of the far-field waves) of about 0 and about pi/2.

Collins, William↗
NASA NTRS1989

Acceleration of thermal plasma in the magnetosphere

Analytic theory and numerical simulations are used here to investigate the physics of two types of mixed plasmas. The transverse acceleration of ions on auroral field lines is considered in order to determine the effects of multiion species. In the auroral zone the components of a multiion plasma, including hydrogen and oxygen, interact with each other as well as with a two-component electron plasma composed of both a magnetospheric beam and background ionospheric components. This interaction occurs as a mixed ion-ion hybrid mode. How an electron plasma, with both hot and cold components as well as ion beams, affects the plasma sheet boundary layer is examined. It is found that in the presence of this mixed electron plasma, warm ion beams can drive the electron acoustic instability; this phenomenon may be responsible for broadband electrostatic noise in the boundary layer.

Ashour-Abdalla, Maha↗
NASA NTRS1990

HD 51956 - A supergiant in an interacting binary

IUE ultraviolet spectral observations reveal that the F supergiant HD 51956 contains a hot companion star partially obscured by warm plasma. Variable absorption features are analogous to those in the strongly interacting system HD 207739. The F type component is apparently transferring matter to a subluminous B type star which originally was the primary component.

Parsons, Sidney B.↗
NASA NTRS1991

Particle flows to shape and voltage surface discontinuities in the electron sheath surrounding a high voltage solar array in LEO

This paper discusses the numerical modeling of electron flows from the sheath surrounding high positively biased objects in LEO (Low Earth Orbit) to regions of voltage or shape discontinuity on the biased surfaces. The sheath equations are derived from the Two-fluid, Warm Plasma Model. An equipotential corner and a plane containing strips of alternating voltage bias are treated in two dimensions. A self-consistent field solution of the sheath equations is outlined and is pursued through one cycle. The electron density field is determined by numerical solution of Poisson's equation for the electrostatic potential in the sheath using the NASCAP-LEO relation between electrostatic potential and charge density. Electron flows are calculated numerically from the electron continuity equation. Magnetic field effects are not treated.

Metz, Roger N.↗
NASA NTRS1994

Perpendicular electron heating by absorption of auroral kilometric radiation

We investigate the possibility of perpendicular heating of electrons and the generation of '90 deg -electron conics' by particle diffusion in velocity space due to wave-particle interaction with intense auroral kilometric radiation. This interaction is made possible by the downward shift in the R-X cutoff below the electron cyclotron frequency that occurs in the presence of warm plasma. We stimulate this condition and solve the diffusion equation using a finite difference algorithm. The results show strong perpendicular electron heating and indicate that the main characteristics of an electron conic distribution can be reproduced under these conditions.

Morgan, D. D.↗
NASA NTRS2016

Revisiting the Inner Magnetospheric Oxygen Torus with DE 1 RIMS

Nearly 35 years ago direct observations of cold plasmaspheric ions found enhanced O(+), O(++), and even N(+) densities in the outer plasmasphere, in particular during storm recovery conditions. Enhancements were seen inside or just outside of the plasmapause at all magnetic local times. Whereas nominal O(+) concentrations were found to be 1% or less inside the plasmasphere, enhanced O(+) in the vicinity of the plasmapause was found to reach densities comparable to H(+). Enhanced ion outflow (including oxygen) from high latitudes has also become part of our picture of storm-time phenomena. More recently it has become apparent that high latitude outflow is a source of inner magnetospheric warm ions that convect into morning and afternoon local times, to form what we now call the warm plasma cloak. Low to middle latitude ionospheric outflow and high latitude outflow are thought to result from very different processes and can be expected to contribute differently as a function of conditions and locations to the dynamic processes of energy and particle transport in the inner magnetosphere. Given the apparent proximity of their delivery to the vicinity of the plasmapause during plasmaspheric refilling conditions it becomes worthwhile to question the origin of the oxygen torus and its role in this region. While the observations do not yet exist to settle this question, there are measurements that contribute to the discussion in the new emerging context of cold plasma in the inner magnetosphere. In this paper we present and discuss DE 1 RIMS derived ion densities and temperatures that contribute to answering these outstanding questions about the origin and dynamics of the oxygen torus.

stormtime↗
NASA NTRS2017

Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and Their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm

The magnetic storm that commenced on June 22, 2015 was one of the largest storms in the current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated interplanetary shock waves. On June 22 at 18:36 UT the magnetosphere was impacted by the leading-edge shock wave and a sheath carrying a large and highly variable interplanetary magnetic field (IMF) Bz with values ranging from +25 to -40 nT. During the subsequent interval from 0000 to 0800 UT, there was a second intensification of the geomagnetic storm resulting from the impact of the CME. We present dramatic responses of simultaneous particle measurements from the high-altitude Magnetospheric Multiscale Mission (MMS) at high altitudes in the magnetosphere (approx. 9-12 Re) and from the low-altitude (F-region) Floating Potential Measurement Unit (FPMU) on board the International Space Station (ISS). We analyze potential causes of these dramatic particle flux dropouts by putting them in the context of storm-time electrodynamics, and support our results with numerical simulations of the global magnetosphere and ionosphere. During the sheath phase of the storm, the MMS spacecraft in the near-earth equatorial plane observed a rapid reconfiguration of the magnetic field near 1923 UT. Initially in the warm plasma sheet, particle flux dropouts were observed as they tracked the plasma-sheet to lobe transitions with the stretching and thinning of the plasma sheet. Anti-sunward flowing O+ ions of ionospheric origin were also measured during this period, confirming that the MMS spacecraft temporarily was in a lobe.

Coffey, Victoria↗
DOE OSTI2022

Modeling Cosmic Reionization

The transformation of cold neutral intergalactic hydrogen into a highly ionized warm plasma marks the end of the cosmic dark ages and the beginning of the age of galaxies. The details of this process reflect the nature of the early sources of radiation and heat, the statistical characteristics of the large-scale structure of the Universe, the thermodynamics and chemistry of cosmic baryons, and the histories of star formation and black hole accretion. A number of massive data sets from new ground- and space-based instruments and facilities over the next decade are poised to revolutionize our understanding of primeval galaxies, the reionization photon budget, the physics of the intergalactic medium (IGM), and the fine-grained properties of hydrogen gas in the "cosmic web". In this review we survey the physics and key aspects of reionization-era modeling and describe the diverse range of computational techniques and tools currently available in this field.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Unraveling electronic correlations in warm dense quantum plasmas

The study of matter at extreme densities and temperatures has emerged as a highly active frontier at the interface of plasma physics, material science and quantum chemistry with relevance for planetary modeling and inertial confinement fusion. A particular feature of such warm dense matter is the complex interplay of Coulomb interactions, quantum effects, and thermal excitations, making its rigorous theoretical description challenging. Here, we demonstrate how ab initio path integral Monte Carlo simulations allow us to unravel this intricate interplay for the example of strongly compressed beryllium, focusing on two X-ray Thomson scattering data sets obtained at the National Ignition Facility. We find excellent agreement between simulation and experiment with a very high level of consistency between independent observations without the need for any empirical input parameters. Our results call into question previously used chemical models, with important implications for the interpretation of scattering experiments and radiation hydrodynamics simulations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Simulation of a strong steady-state plasma shock in a warm dense matter regime

The structure of collisional plasma shocks has been subject to an extensive, multi-decadal investigation—in the hydrodynamic, hybrid kinetic ion/electron fluid, and fully kinetic ion/electron limits. Despite this thoroughness, all of these studies apply exclusively to classical, weakly coupled plasmas. Here, we report the first results for a planar hydrodynamic simulation of a strong, steady-state shock in a subspace of the warm dense matter (WDM) regime. Specifically, we consider a plasma of fully degenerate electrons with moderate-to-strongly coupled ions. Since the WDM ion and electron transport coefficients and equation of state differ markedly from their non-degenerate, weak-coupling equivalents, we find that the structure of a WDM plasma shock notably deviates from the ideal plasma picture.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Interspecies radiative transition in warm and superdense plasma mixtures

Superdense plasmas widely exist in planetary interiors and astrophysical objects such as brown-dwarf cores and white dwarfs. How atoms behave under such extreme-density conditions is not yet well understood, even in single-species plasmas. Here, we have applied thermal density functional theory to investigate the radiation spectra of superdense iron–zinc plasma mixtures at mass densities of ρ = 250 to 2000 g cm -3 and temperatures of kT = 50 to 100 eV, accessible by double-shell–target implosions. Our ab initio calculations reveal two extreme atomic-physics phenomena—firstly, an interspecies radiative transition; and, secondly, the breaking down of the dipole-selection rule for radiative transitions in isolated atoms. Our first-principles calculations predict that for superdense plasma mixtures, both interatomic radiative transitions and dipole-forbidden transitions can become comparable to the normal intra-atomic Kα-emission signal. These physics phenomena were not previously considered for extreme high-density plasma mixtures at super-high energy densities.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1985

Resonance cone structure in a warm inhomogeneous bounded plasma with lower-hybrid resonance layers

The paper presents a theoretical study of the problem of the wave fields excited by a gap source at the edge of an inhomogeneous magnetized plasma with a pair of lower-hybrid resonance layers present and bounded by conducting walls. The approach used is that of a solution as a sum of multiply reflected extraordinary mode and ion-thermal resonance cones as an alternative to the guided-wave mode approach. A diagrammatic scheme for writing the solution is given which can be used to determine in great detail the structure and properties of the resonance cones and the way they transform across the back-to-back hybrid layers. Evanescent resonance cones are shown to exist in the high-density region between the hybrid resonance layers and to tunnel through to the other side, maintaining this general structure if the layer is relatively thin.

Grabbe, C. L.↗
DOE OSTI2023

Polarization and properties of low-frequency waves in warm magnetized two-fluid plasma

This paper presents the derivation of a general wave dispersion relation for warm magnetized plasma under the two-fluid formalism. The discussion is quite general except for the assumption of low frequency and slow phase speed, for which the displacement current is negligible, under the implicit assumption that the plasma is sufficiently dense to satisfy the condition ωpe>ωce, where ωpe and ωce denote the plasma oscillation frequency and electron gyro frequency, respectively. The present discussion does not invoke charge neutrality associated with the fluctuations although it is implicitly satisfied. The resulting dispersion relation that includes the fluid thermal effects shows that there are three eigen modes, which include those corresponding to ideal MHD, namely, fast, slow, and kinetic Alfvén waves, as well as higher-frequency modes including the ion and electron cyclotron and lower-hybrid resonances. The fluid effects in the ideal MHD wave branches are influenced by the finite Larmor radius scales, and when the wave number in the cross field direction is comparable to these values, the fluid effects become significant. It is found that the Larmor radius should be interpreted in the sense as ion-acoustic gyro-radius instead of ion thermal gyro radius only. That is, it is found that the electrons also contribute to the non-ideal effect associated with the kinetic Alfvén wave. A comprehensive explanation of the polarization of each mode is also presented. The present findings indicate that the polarity may change its sign only for the kinetic Alfvén mode branch and that such a transition is based on the propagation angle. When such a change does take place, it is found that the kinetic Alfvén wave transits to an ion-acoustic mode. For each branch, it is also found that the electric field along the ambient magnetic field is purely transverse.

Physics↗