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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

The Faraday Effect Tracker of Coronal and Heliospheric Structure (FETCH) Instrument

There continue to be open questions regarding the solar wind and coronal mass ejections (CMEs). For example: how do magnetic fields within CMEs and corotating/stream interaction regions (CIRs/SIRs) evolve in the inner heliosphere? What is the radially distributed magnetic profile of shock-driving CMEs? What is the internal magnetic structure of CMEs that cause magnetic storms? It is clear that these questions involve the magnetic configurations of solar wind and transient interplanetary plasma structures, for which we have limited knowledge. In order to better understand the origin of the magnetic field variability in steady-state structures and transient events, it is necessary to probe the magnetic field in Earth-directed structures/disturbances. This is the goal of the Multiview Observatory for Solar Terrestrial Science (MOST) mission (Gopalswamy et al., 2022). For MOST to answer the aforementioned questions, we propose the instrument concept of the Faraday Effect Tracker of Coronal and Heliospheric structures (FETCH), a simultaneous quad-line-of-sight polarization radio remote-sensing instrument. With FETCH, spacecraft radio beams passing through the Sun–Earth line offer the possibility of obtaining information of plasma conditions via analysis of radio propagation effects such as Faraday rotation and wave dispersion, which provide information of the magnetic field and total electron content (TEC). This is the goal of the FETCH instrument, one of ten instruments proposed to be hosted on the MOST mission. The MOST mission will provide an unprecedented opportunity to achieve NASA’s heliophysics science goal to “explore and characterize the physical processes in the space environment from the Sun” (Gopalswamy et al., 2022).

Solar corona↗
DOE OSTI2024

Quasilinear theory: the lost ponderomotive effects and why they matter

Quasilinear theory (QLT) has been used for modeling wave–plasma interactions for decades but remains largely heuristic. Plasma inhomogeneity, ponderomotive effects, microscopic fluctuations, and collisions are not easily accommodated from first principles in QLT, and typically are ignored entirely, due to the limitations of the standard Fourier–Laplace global-mode approach. This results in inconsistencies, for example, violation of the action conservation for nonresonant waves. However, these issues can be avoided, and the theory can be substantially generalized and corrected, if QLT is formulated using more suitable analytical tools, particularly, the Weyl symbol calculus. Here, an attempt is made to deliver an accessible review of this modern formulation, provide intuitive calculations for special cases, and elaborate on the connection with the ‘oscillation-center QLT’ originally proposed by Dewar (Phys Fluids 16:1102, 1973). A Fokker–Planck equation for a ‘dressed’ distribution is derived from the Klimontovich equation and captures quasilinear diffusion, ponderomotive forces, and interactions with background fields for a generic Hamiltonian, so many known formulations of QLT for specific plasma models become corollaries of a single unifying theory. Also, waves are allowed to be off-shell (not constrained by a dispersion relation), which allows them to accommodate microscopic fluctuations. This leads to a collision integral of the Balescu–Lenard type that has all the usual properties but is not restricted to any specific plasma model. For on-shell waves, a generalized version of the classic oscillation-center QLT is obtained. Finally, combined with the wave-kinetic equation, this formulation not only conserves particles, momentum, and energy, like the classic QLT but also reinstates the action conservation for nonresonant waves.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1992

Nonadiabatic heating of the central plasma sheet at substorm onset

Heating events in the plasma sheet boundary layer and central plasma sheet are found to occur at the onset of expansive phase activity. The main effect is a dramatic increase in plasma temperature, coincident with a partial dipolarization of the magnetic field. Fluxes of energetic particles increase without dispersion during these events which occur at all radial distances up to 23 RE, the apogee of the ISEE spacecraft. A major difference between these heating events and those observed at geosynchronous distances lies in the heating mechanism which is nonadiabatic beyond 10 RE but may be adiabatic closer to earth. The energy required to account for the increase in plasma thermal energy is comparable with that required for Joule heating of the ionosphere. The plasma sheet must be considered as a major sink in the energy balance of a substorm. Lobe magnetic pressures during these events are estimated. Change in lobe pressure are generally not correlated with onsets or intensifications of expansive phase activity.

Huang, C. Y.↗
NASA NTRS1985

Whistler damping at oblique propagation - Laminar shock precursors

This paper addresses the collisionless damping of whistlers observed as precursors standing upstream of oblique, low-Mach number terrestrial bow shocks. The linear theory of electromagnetic waves in a homogeneous Vlasov plasma with Maxwellian distribution functions and a magnetic field is considered. Numerical solutions of the full dispersion equation are presented for whistlers propagating at an arbitrary angle with respect to the magnetic field. It is demonstrated that electron Landau damping attenuates oblique whistlers and that the parameter which determines this damping is beta-e. In a well-defined range of parameters, this theory provides damping lengths which are the same order of magnitude as those observed. Thus electron Landau damping is a plausible process in the dissipation of upstream whistlers. Nonlinear plasma processes which may contribute to precursor damping are also discussed, and criteria for distinguishing among these are described.

Gary, S. P.↗
NASA NTRS1997

Alfvenic Solitons in Ultrarelativistic Electron-Position Plasmas

In electron-positron plasmas some of the plasma modes are decoupled due to the equal charge-to-mass ratio of both species. We derive the dispersion law for a low-frequency, generalized X-mode, which exists at all angles of propagation with respect to the static magnetic field.

Electron-positron plasmas Pulsars Nonlinear Modes↗
NASA NTRS1970

Dispersion discontinuities of strong collisionless shocks

Linear fluid equations are used to estimate wave train properties of strong collisionless shocks. Fast shocks exhibit several dispersion changes with increasing Mach number. For perpendicular propagation into a finite-beta plasma, an ion cyclotron radius trailing wave train exists only for (M sub F)2 is smaller than 2. Oblique fast shocks have a leading ion inertia wave train if M sub A is smaller than root of M(+)/M(-) cos theta/2 and a trailing electron inertia train if M sub A is greater than root of M(+)/M(-) cos theta/2. If the downstream sound speed exceeds the flow speed, linear wave theory predicts a trailing ion acoustic structure which probably resides within the magnetic shock. For a turbulent shock model in which an effective electron-ion collision frequency exceeds the lower hybrid frequency, ions decouple from the magnetic field; the shock wave train now trails with electron inertia and electron gyroradius lengths. Comparisons of this turbulent model and observations on the earth's bow shock are made.

Coroniti, F. V.↗
NASA NTRS1975

Linear theory of equatorial spread F

A fluid dispersion relation for the drift and interchange (Rayleigh-Taylor) modes in a collisional plasma forms the basis for a linear theory of equatorial spread F. The collisional-drift-mode growth rate will exceed the growth rate of the Rayleigh-Taylor mode at short perpendicular wavelengths and density-gradient scale lengths. The drift mode can grow on the top-side as well as the bottom-side density gradients. It is concluded that below the F peak where spread F predominates, both the drift and Rayleigh-Taylor modes contribute to the total spread F spectrum, with the Rayleigh-Taylor mode dominating at long and the drift mode at short perpendicular wavelengths above the ion Larmor radius.

Hudson, M. K.↗
NASA NTRS1981

Discrete breakup arcs and kinetic Alfven waves

Attention is confined to the extremely narrow auroral structures whose characteristic dimensions perpendicular to the magnetic fields are of the order of several hundred meters or even less. The starting point of the model used here is the assumption that discrete breakup arcs are caused by a change in the magnetosphere convection pattern that is localized in space. Particular attention is given to the shear Alfven mode. It is proposed that discrete breakup arcs are a direct manifestation of kinetic interaction between charged particles and an 'mhd' perturbation. It is stressed that the model applies only to narrow structures (thickness of the order of the plasma skin depth) and to short-lived phenomena (time scales shorter than a dispersion time). It is shown that a change of convection pattern in a spatially limited region leads to the emission of a shear-Alfven wave packet which propagates along the magnetic field line with a characteristic velocity.

Goertz, C. K.↗
NASA NTRS1984

Correlation of auroral hiss and upward electron beams near the polar cusp

Data were obtained from the DE-1 high-altitude plasma instrument (HAPI) and plasma wave instrument (PWI) during outbound passes through the polar cusp near local noon. The observed distribution functions of electron beams are fitted by drifting Maxwellian functions and the observed distribution functions of hot background electrons by isotropic Maxwellian functions. In addition, the cold plasma density is inferred from knowledge of the electron plasma frequency and the measured density of the warm plasma, including the electron beam distribution. The empirically fitted plasma parameters, including density, temperature and drifting energy, are used to solve the linear dispersion equation for the resulting whistler mode emissions. Because the whistler mode becomes quasi-electrostatic for wave-normal angles near the resonance cone, the electrostatic approximation is used for the whistler mode dispersion relation. The results of wave instability analyses are then compared with the wave observations. A ray tracing of cusp hiss emission is conducted to locate the wave source region (at about one earth-radius).

Lin, C. S.↗
NASA NTRS1994

Multiple Hollow Cathode Wear Testing for the Space Station Plasma Contactor

A wear test of four hollow cathodes was conducted to resolve issues associated with the Space Station plasma contactor. The objectives of this test were to evaluate unit-to-unit dispersions, verify the transportability of contamination control protocols developed by the project, and to evaluate cathode contamination control and activation procedures to enable simplification of the gas feed system and heater power processor. These objectives were achieved by wear testing four cathodes concurrently to 2000 hours. Test results showed maximum unit-to-unit deviations for discharge voltages and cathode tip temperatures to be +/-3 percent and +/-2 percent, respectively, of the nominal values. Cathodes utilizing contamination control procedures known to increase cathode lifetime showed no trends in their monitored parameters that would indicate a possible failure, demonstrating that contamination control procedures had been successfully transferred. Comparisons of cathodes utilizing and not utilizing a purifier or simplified activation procedure showed similar behavior during wear testing and pre- and post-test performance characterizations. This behavior indicates that use of simplified cathode systems and procedures is consistent with long cathode lifetimes.

Soulas, George C.↗
NASA NTRS1995

Evaluation of Pd-Cr Wires for Strain Gage Application

A newly developed alloy, palladium-13 weight percent chromium (Pd13Cr), was identified by United Technologies Research Center under a NASA contract to be the best material for high temperature strain gage applications. An electrical resistance strain gage that can provide accurate static strain measurement to a temperature higher than that of a commercially available gage is urgently needed in aerospace and aeronautics research. A strain gage made of a 25.4 micron (1 mil) diameter Pd13Cr wire has been recently demonstrated to be usable for static strain measurements to 800 C. This compares to the 400 C temperature limit of the commercially available strain gages. The performance of the Pd-Cr gage, however, strongly depends on the quality of the Pd13Cr wire. Four batches of Pd-Cr wires purchased from three different manufacturers were therefore evaluated to determine the best source of the wire for strain gage applications. The three suppliers were Precious Metal Institute in China, Sigmund Cohn Co., and G & S Titanium, Inc. in the United States. Two batches of wires obtained from Previous Metal Institute in 1987 and 1992, respectively are referred to herein as China87 and China92 wires. The mechanical, chemical and electrical properties of these wires, both as-received and after high temperature exposures at 800 C for 50 hours were analyzed. The elastic modulus and the failure strength of the wires were evaluated using a tensile test machine equipped with a laser speckle strain measurement system. The chemical and microstructural properties of the wires were inspected using a plasma atomic emission spectrometer and a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscope (EDS). The electrical stability and repeatability of the wires were determined by measuring the electrical resistance of the wires during three thermal cycles to 1000 C and a ten-hour soak at 1000 C. As a result of this study, the wire which has the highest strength, the least impurities content, the best oxidation resistance and the best electrical stability will be selected for upcoming strain gage applications.

Lei, Jih-Fen↗
NASA NTRS1975

Finite difference methods for transient signal propagation in stratified dispersive media

Explicit difference equations are presented for the solution of a signal of arbitrary waveform propagating in an ohmic dielectric, a cold plasma, a Debye model dielectric, and a Lorentz model dielectric. These difference equations are derived from the governing time-dependent integro-differential equations for the electric fields by a finite difference method. A special difference equation is derived for the grid point at the boundary of two different media. Employing this difference equation, transient signal propagation in an inhomogeneous media can be solved provided that the medium is approximated in a step-wise fashion. The solutions are generated simply by marching on in time. It is concluded that while the classical transform methods will remain useful in certain cases, with the development of the finite difference methods described, an extensive class of problems of transient signal propagating in stratified dispersive media can be effectively solved by numerical methods.

Lam, D. H.↗
NASA NTRS1991

Structure and dynamics of the Uranian magnetotail - Results from hot plasma and magnetic field observations

Analysis of Voyager 2 low-energy charged particle and magnetic field data in the Uranian magnetotail show that this system has many features similar to those seen at earth. Isotropization of core magnetosphere 28-43 keV ions has been observed at the trapping boundary upon entry into the magnetotail near L = 17, an effect seen in ion populations at earth and attributed to neutral sheet scattering. An extensive and persistent plasma sheet boundary layer is found to contain field-aligned ion streams with a variety of angular and energetically dispersive effects. Streaming distributions in the magnetotail horn region map to the auroral emission region observed by the Voyager ultraviolet spectrometer. A quiet-time near-tail region is distinguished from a distant disturbed region, where evidence of a substorm is observed. There is evidence suggesting that the distant plasma sheet is not corotating with the planet.

Kane, M.↗
NASA NTRS1994

Mode properties of low-frequency waves: Kinetic theory versus Hall-MHD

In fluid theory, the ordering of low-frequency modes in a homogeneous plasma is based on the phase velocity, since modes do not intersect each other in dispersion diagrams as a function of wavenumber or other parameters. In linear kinetic theory, modes cross each other. Thus a consistent and useful classification should be based on the physical properties of the modes instead. This paper attempts such a classification by documeting the dispersion and general mode properties of the low-frequency waves (omega much less than (OMEGA(sub ci) OMEGA(sub ce) (exp 1/2)), where OMEGA(sub ci), OMEGA(sub ce) are the cyclotron frequencies of the ions and electrons, respectively) in kinetic theory, and by comparing them to the results of two-fluid theory. Kinetic theory gives a seperate Alfven/ion-cyclotron (A/IC) wave with phase speed Omega/k approximately = v(sub A) cos theta for omega much less than OMEGA(sub ci), where v(sub A) is the Alfven velocity and theta the angle of propagation between wave vector k and background magnetic field B(sub o). For a given wavenumber, the magnetosonic mode is a double-valued solution with a singular point in theta, beta parameter space, where beta is the ratio of thermal pressure to magnetic pressure. It is shown that a branch cut starting at the singular point theta approximately 30 deg, beta approximately 3 and leading to larger beta gives a practical and consitent seperation of this double-valued magnetosonic solution. Selection of this branch cut results in a moderately damped fast/magnetos onic and a heavily damped slow/sound wave. A comprehensive review of the polarization, compressibility and other mode properties is given and shown to be consistent with the selected branch cut. At small wavenumbers, the kinetic mode properties typically start to deviate significantly from their fluid counterparts at beta approximately 0.5. At larger beta, there is no longer a consistent correspondence between the fluid and kinetic modes. Kinetic theory also dictates the use of different mode properties to distinguish between them in observational data. For example, the phase between the density and magnetic field perturbation may become useless at high beta, whereas the direction of the magnetic field perturbations with respect to k and B(sub o) remains a useful characteristic. Two quantities based on this characteristic are suggested and are shown to be useful also to distinguish between the mirror mode and A/IC waves in a plasma with temperature anisotropy.

Krauss-Varban, D.↗
DOE OSTI2024

Net lithium deposition and dominant self-sputtering in lithium tokamak experiment-β with a liquid lithium wall

We observed enhanced net lithium deposition and lithium erosion, possibly dominated by physical sputtering of lithium by lithium-ion bombardment, on the outer plasma-facing surface in the Lithium Tokamak eXperiment-β (LTX-β) during liquid lithium wall operations. Silicon crystal samples with micro-trenches (30 μm × 30 μm × 2–7 μm deep) were exposed to hydrogen plasmas in LTX-β for solid and liquid lithium wall operations. Post-mortem analysis using X-ray photoelectron spectroscopy combined with argon ion sputtering measured net lithium deposition of 8.2 or 21 nm on the silicon crystal surface exposed for ~ 50 repeated shots of ~ 50-ms hydrogen plasma discharges during the liquid lithium wall operations at a vessel temperature of 475 K. Energy dispersive X-ray spectroscopy measured oxygen concentration patterns on the micro-trench floors, which were due to oxidized lithium deposition. Using the inhomogeneous oxygen concentration pattern caused by an ion-shadowing effect associated with the micro-trench’s geometric structure, we determined a polar incident ion direction of 68.4 ± 1.6° referenced to the surface normal direction. This observation was well-explained by the hypothesis that self-sputtering of Li was a dominant lithium erosion source in addition to lithium sputtering by hydrogen bombardment.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1994

Low and middle altitude cusp particle signatures for general magnetopause reconnection rate variations. 1: Theory

We present predictions of the signatures of magnetosheath particle precipitation (in the regions classified as open low-latitude boundary layer, cusp, mantle and polar cap) for periods when the interplanetary magnetic field has a southward component. These are made using the 'pulsating cusp' model of the effects of time-varying magnetic reconnection at the dayside magnetopause. Predictions are made for both low-altitude satellites in the topside ionosphere and for midaltitude spacecraft in the magnetosphere. Low-altitude cusp signatures, which show a continuous ion dispersion signature, reveal 'quasi-steady reconnection' (one limit of the pulsating cusp model), which persists for a period of at least 10 min. We estimate that 'quasi-steady' in this context corresponds to fluctuations in the reconnection rate of a factor of 2 or less. The other limit of the pulsating cusp model explains the instantaneous jumps in the precipitating ion spectrum that have been observed at low altitudes. Such jumps are produced by isolated pulses of reconnection: that is, they are separated by intervals when the reconnection rate is zero. These also generate convecting patches on the magnetopause in which the field lines thread the boundary via a rotational discontinuity separated by more extensive regions of tangential discontinuity. Predictions of the corresponding ion precipitation signatures seen by midaltitude spacecraft are presented. We resolve the apparent contradiction between estimates of the width of the injection region from midaltitude data and the concept of continuous entry of solar wind plasma along open field lines. In addition, we reevaluate the use of pitch angle-energy dispersion to estimate the injection distance.

Lockwood, M.↗
NASA NTRS1994

Quiet-time intensifications along the poleward auroral boundary near midnight

Radar and optical measurements from Sondrestrom are combined with satellite and Goose Bay data in a study of the poleward edge of the nightside auroral oval during a quiet period. The B(sub y) and B(sub z) components of the interplanetary magnetic field were close to zero, and the B(sub x) component was approximately 8 nT for more than 24 hours. On a large scale, the convection and precipitation patterns remained almost constant during this period; on a small scale, however, the conditions were quite dynamic. At 10- to 20-min intervals the arc that marked the poleward auroral boundary intensified, and a new arc appeared poleward of it. About once per hour, stronger intensifications were observed. One such event is examined in detail. The auroral arcs first appeared to dim, and then they brightened, with a factor of 10 increase in E region electron density. At the time of the brightening a new arc formed poleward of all the arcs. The arcs then drifted southward at velocities of approximately 270 m/s. A plasma drift disturbance, characterized by a doubling of the southward velocity and a reversal in the east-west component, propagated westward at 900 m/s through the fields of view of the Sondrestrom and Goose Bay radars. A simultaneous satellite overpass close to the radars revealed the presence of an energetic ion event similar to the 'velocity dispersed ion structures' observed on the Aureol satellite and presumed to be the signature of fast ion beams within the plasma sheet boundary layer. The stronger arc intensification events observed by the Sondrestrom radar are associated with an increase in plasma flow across the boundary between open and closed magnetic field lines. We interpret this increased flow as the ionospheric signature of abrupt, localized increases in the reconnection rate in the midnight sector.

De La Beaujardiere, O.↗
NASA NTRS1995

Penetration of the interplanetary magnetic field B(sub y) magnetosheath plasma into the magnetosphere: Implications for the predominant magnetopause merging site

Magnetosheath plasma peertated into the magnetospere creating the particle cusp, and similarly the interplanetary magnetic field (IMF) B(sub y) component penetrates the magnetopause. We reexamine the phenomenology of such penetration to investigate implications for the magnetopause merging site. Three models are popular: (1) the 'antiparallel' model, in which merging occurs where the local magnetic shear is largest (usually high magnetic latitude); (2) a tilted merging line passing through the subsolar point but extending to very high latitudes; or (3) a tilted merging line passing through the subsolar point in which most merging occurs within a few Earth radii of the equatorial plane and local noon (subsolar merging). It is difficult to distinguish between the first two models, but the third implies some very different predictions. We show that properties of the particle cusp imply that plasma injection into the magnetosphere occurs most often at high magnetic latitudes. In particular, we note the following: (1) The altitude of the merging site inferred from midaltitude cusp ion pitch angle dispersion is typically 8-12 R(sub E). (2) The highest ion energy observable when moving poleward through the cusp drops long before the bulk of the cusp plasma is reached, implying that ions are swimming upstream against the sheath flow shortly after merging. (3) Low-energy ions are less able to enter the winter cusp than the summer cusp. (4) The local time behavior of the cusp as a function of B(sub y) and B(sub z) corroborates predictions of the high-latitude merging models. We also reconsider the penetration of the IMF B(sub y) component onto closed dayside field lines. Our approach, in which closed field lines ove to fill in flux voids created by asymmetric magnetopause flux erosion, shows that strich subsolar merging cannot account for the observations.

Newell, Patrick T.↗