Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “PLASMA COMPOSITION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Lower Hybrid Frequency Range Waves Generated by Ion Polarization Drift Due to Electromagnetic Ion Cyclotron Waves: Analysis of an Event Observed by the Van Allen Probe B

We analyze a wave event that occurred near noon between 07:03 and 07:08 UT on 23 February 2014 detected by the Van Allen Probes B spacecraft, where waves in the lower hybrid frequency range (LHFR) and electromagnetic ion cyclotron (EMIC) waves are observed to be highly correlated, with Pearson correlation coefficient of approximately 0.86. We assume that the correlation is the result of LHFR wave generation by the ions polarization drift in the electric field of the EMIC waves. To check this assumption the drift velocities of electrons and H+, He+, and O+ ions in the measured EMIC wave electric field were modeled. Then the LHFR wave linear instantaneous growth rates for plasma with these changing drift velocities and different plasma compositions were calculated. The time distribution of these growth rates, their frequency distribution, and the frequency dependence of the ratio of the LHFR wave power spectral density (PSD)parallel and perpendicular to the ambient magnetic eld to the total PSD were found. These characteristics of the growth rates were compared with the corresponding characteristics of the observed LHFR activity. Reasonable agreement between these features and the strong correlation between EMIC and LHFR energy densities support the assumption that the LHFR wave generation can be caused by the ions polarization drift in the electric field of an EMIC wave.

Van Allen Probes↗
NASA NTRS1985

Substorm effects on the plasma sheet ion composition on March 22, 1979 (CDAW 6)

One of the potentially most useful aspects of mass spectroscopy in magnetospheric research is related to the ability to distinguish between ions of solar wind and terrestrial origins. Knowing the source of the plasmas in various regions and under various geomagnetic conditions is crucial in improving the understanding of particle flows in the magnetosphere. Sharp et al. (1982) found that the plasma sheet ions in the 0.1- to 16-keV/e range, were predominantly of solar wind origin during low geomagnetic activity, while there was a large terrestrial component during active times. This paper presents a set of data from March 22, 1979. The reported investigation represents the first detailed case study of the relation between geomagnetic substorm activity and the ion composition in the plasma sheet. A decrease in solar wind ion flow at ISEE 1 and the subsequent increase in the flow of ionospheric ions is interpreted as evidence of a fundamental change in the particle flow pattern following the start of substorm activity.

Lennartsson, W.↗
NASA NTRS1986

ISEE observations of the plasma sheet boundary, plasma sheet, and neutral sheet. I - Electric field, magnetic field, plasma, and ion composition

The first simultaneous study of dc and ac electric and magnetic fields, E x B velocity, plasma flows, ratio of plasma to magnetic field pressure, total energy density, energetic particles, and ion composition from the ISEE satellites and ground and interplanetary magnetic fields has been made to determine (1) the relationship of the previously observed electric fields at the plasma sheet boundary and at the neutral sheet to plasma parameters, and (2) whether the phenomena occurring during quiet and active times were consistent with the formation of a near-earth neutral line during substorms or with the boundary layer model. Five observations made during the study of two substorms were seen to be in agreement with the neutral-line model. The observations are consistent with the satellite being located at varying distances from the neutral line and diffusion region where reconnection and plasma acceleration were occurring. Although the z component (into or out of the ecliptic plane) of E x B convection was generally toward the neutral sheet, there were examples when it was consistent with the inferred motion of the plasma sheet past the satellite. A synthesis of previous reports on large electric fields at the plasma sheet boundary and variable fields at the neutral sheet including the associated plasma flows is also described.

Cattell, C. A.↗
NASA NTRS1993

International Reference Ionosphere: Past, present, and future. I - Electron density. II - Plasma temperatures, ion composition and ion drift

The most important investigations leading to the International Reference Ionosphere 1990 (IRI-90) are overviewed, and the latest version of the model is described. The shortcomings and limitations of the IRI-90 are pointed out, together with the ways of overcoming them. The list of studies that the IRI group has yet to carry out includes the investigations of magnetic storm effects as the highest priority. This paper discusses determinations of and the available data on the electron density, plasma temperatures, ion composition, and ion drift in the ionosphere, together with future improvements needed on these parameters.

Bilitza, D.↗
NASA NTRS1987

Dynamical features of the plasma-sheet ion composition, density, and energy

The effects of changes in solar and geomagnetic activity on the major plasma-sheet ions are investigated on the basis of a statistical analysis of 1500 h of data obtained at distances 10-23 earth radii and energy/charge ratios 0.1-16 keV/e by the ISEE-1 energetic-ion mass spectrometer. The results are presented in extensive graphs and discussed in detail. It is found that substorm activity is accompanied by a significant decrease in the density of solar-origin H(+) ions, a sharp increase in the energy per nucleon of both H(+) and He(+) ions, and an increase in the density of terrestrial O(+) ions. A factor-of-three increase in the overall O(+) density over the observation period is attributed to an increase in the solar EUV flux.

Lennartsson, W.↗
NASA NTRS1981

Composition of hot ions /0.1-16 keV/e/ as observed by the GEOS and ISEE mass spectrometers and inferences for the origin and circulation of magnetospheric plasmas

The composition of hot magnetospheric plasma through different regions of the magnetosphere is described on the basis of mass spectrometer measurements by the GEOS 1, GEOS 2, and ISEE-1 spacecraft. Coordinated composition measurements on the different spacecraft also provide information on the spatial and temporal characteristics of the plasma during storms. Data on ion origins are also provided.

Balsiger, H.↗
NASA NTRS1986

Transverse auroral ion energization observed on DE-1 with simultaneous plasma wave and ion composition measurements

Simultaneous high-time-resolution plasma-wave and ion-composition measurements obtained with DE-1 during a magnetospheric-cusp crossing on March 15, 1984 and during an evening auroral-zone crossing on January 4, 1984 are reported. The data are presented graphically and characterized in detail, with a focus on the transverse energization of H(+) and O(+) ions. An O(+) distribution observed during the cusp crossing is shown to be well represented by a bi-Maxwellian distribution with temperatures 180 eV parallel and 250 eV perpendicular to the local magnetic field and a bulk flow velocity of 27 km/s up the magnetic-field line. In the auroral-zone data a simultaneous transverse-energy increase is detected in both H(+) and O(+) components in the presence of plasma-wave emissions at multiples of the hydrogen gyrofrequency.

Peterson, W. K.↗
NASA NTRS1981

Energetic ion composition of the plasma sheet

Data obtained from the energetic ion mass spectrometer experiment on Isee 1 in the distant plasma sheet are presented. These data show that (1) the plasma sheet has a significant and variable ionospheric component (H(+) and O(+)) representing from 10% to more than 50% of the total number density and (2) there is more than one process responsible for the energization of solar wind plasma (H(+) and He(++)) to plasma sheet energies.

Peterson, W. K.↗
NASA NTRS2004

Friction and Wear Characteristics of a Modified Composite Solid Lubricant Plasma Spray Coating

LCR304 is a solid lubricant coating composed of Ni-10Cr, Cr2O3, BaF2-CaF2 and Ag and developed for dimensional stability in high temperature air. This coating is a modification of PS304, which differs in that the Ni-Cr constituent contains 20wt% Cr. The tribological characteristics of LCR304 were evaluated by pin-on-disk and foil air bearing rig testing from 25 to 650 C and compared to previous test results with PS304. For both tests, the friction coefficient decreased as temperature increased from 25 to 650 C. Wear generally decreased with increasing temperature for all pin-on-disk tests. LCR304 coated components produced the least wear of Inconel X-750 counterface materials at 427 and 650 C. These results indicate that the LCR304 coating has potential as a replacement for PS304 in, for example, low cycle (minimum wear) applications where dimensional stability is imperative.

Stanford, M. K.↗
NASA NTRS1992

Giotto data analysis: Electron plasma and heavy ion composition measurements at Comet Halley

This investigation involved the analysis of electron plasma and heavy ion composition measurements made by the COPERNIC (COmplete Positive ion, Electron, and Ram Negative Ion measurements near Comet Halley) plasma experiment during the close fly-by of Halley by the European Space Agency's Giotto spacecraft. The experiment provided measurements of the full 3-dimensional distribution of 10 eV-30 keV electrons, and mass analysis of cold cometary ions from 10-210 amu. The analysis of the COPERNIC data has yielded some remarkable results, including: The discovery of negatively charged ions in the inner coma; the discovery of far heavier (mass is greater than 50 amu) ions than predicted, dominated by complex molecular ions made up of C, H, O, and N; the discovery of an adiabatic heating effect on electrons from the compression of the solar wind plasma; the identification of several organic and sulfur bearing ions; and the discovery of a new 'mystery region' where electrons are accelerated to high energies. These discoveries were in addition to the detailed analysis of 'expected' features at Comet Halley. Although this grant has expired, analysis continues on the data at a low (unfunded) level, and it is expected that more significant results will be obtained. A bibliography of the papers resulting from this research is attached, and a copy of each paper is included.

Lin, Robert P.↗
NASA NTRS2005

Ion Composition in Saturn's Plasma Environment: Early Results from the Cassini Plasma Spectrometer

Prior to Cassini s arrival at Saturn, most of what was known about the composition of the plasma in Saturn s environment was derived from limited measurements by Pioneer 11 and Voyager 1 and 2 in 1979-1981[1-3]. The measurements reported here were made by the Cassini Plasma Spectrometer (CAPS) [4] during the first two Cassini orbits, including the closest approach to Saturn and the rings during the tour, and a close flyby of Titan. The CAPS instrument resolves ion energy/charge from 1 V to 50 kV and ion mass/charge from 1 to approx.100 amu/e, and it measures electron energy from 1 eV to 28 keV. Initial composition measurements of Saturn s magnetosphere show that protons dominate outside approx.8 R(sub s), while inside this radius the plasma is dominated by a mix of water-derived ions and N(+). Over the A and B rings a plasma layer is observed composed of O2(+) and O(+) . The close passage near Titan shows a rich network of both positive and negative molecular ions. We report preliminary analysis of these and other composition findings.

Reisenfeld, D. B.↗
NASA NTRS1977

Composition of the hot plasma near geosynchronous altitude

Although there were no direct measurements of the composition of the hot (keV) plasma at geosynchronous altitudes, the combination of other observations leads to the conclusion that, at least during geomagnetically disturbed periods, there are significant fluxes of ions heavier than protons in this region. Ion composition measurements below 8000 km altitude show upward streaming fluxes of both O(+) and H(+) ions in the L-region of the geosynchronous orbit. These observations are consistent with the conclusion that at least a portion of the total ion fluxes observed at geosynchronous altitude to be highly peaked near the magnetic field lines are heavier than protons and originate in the ionosphere.

Johnson, R. G.↗
NASA NTRS2001

Thermal Conductivity and Thermal Gradient Cyclic Behavior of Refractory Silicate Coatings on SiC/SiC Ceramic Matrix Composites

Plasma-sprayed mullite and BSAS coatings have been developed to protect SiC/SiC ceramic matrix composites from high temperature environmental attack. In this study, thermal conductivity and thermal barrier functions of these coating systems are evaluated using a laser high-heat-flux test rig. The effects of water vapor on coating thermal conductivity and durability are studied by using alternating furnace and laser thermal gradient cyclic tests. The influence of laser high thermal-gradient cycling on coating failure modes is also investigated.

Zhu, Dongming↗
NASA NTRS1993

Protective coatings for high-temperature polymer matrix composites

Plasma-enhanced chemical vapor deposition was used to deposit silicon nitride on graphite-fiber-reinforced polyimide composites to protect against oxidation at elevated temperatures. The adhesion and integrity of the coating were evaluated by isothermal aging (371 C for 500 hr) and thermal cycling. The amorphous silicon nitride (a-SiN:H) coating could withstand stresses ranging from approximately 0.18 GPa (tensile) to -1.6 GPa (compressive) and provided a 30 to 80 percent reduction in oxidation-induced weight loss. The major factor influencing the effectiveness of a-SiN:H as a barrier coating against oxidation is the surface finish of the polymer composite.

Harding, David R.↗
NASA NTRS1980

A Recoverable Plasma Diagnostics Package (RPDP) for Spacelab

The RPDP is a fully instrumented, ejectable and recoverable unit with flight and ground support systems so that it can be utilized attached to the orbiter remote manipulator system, tethered from the orbiter, or as an orbiter subsatellite. Core instruments on the RPDP are flight proven hardware which provide diagnostics measurements of energetic particles, AC electromagnetic and electrostatic waves, vector magnetic field signatures of current systems, vector electric field signatures associated with plasma flow and particle acceleration, thermal plasma ion composition and density, thermal plasma electron density and temperature, and images of optical emissions regions in UV or visible wavelengths.

Shawhan, S. D.↗
NASA NTRS1988

Energetic particles and currents - Results from Dynamics Explorer

The suprathermal plasma instruments on DE 1 and DE 2 (high-altitude plasma instrument, low-altitude plasma instrument, and energetic ion composition spectrometer) have provided new data on the distribution functions and composition of plasmas at altitudes from a few hundred to about 23,000 km. Of particular interest are the results that have been obtained on the injection and transport of plasma in the polar cusp, on the upward acceleration of ionospheric ions and electrons, and on the charge carriers of the various high-latitude Birkeland current systems (using independent measurements of the currents by the magnetic field instruments MAG-A and MAG-B). These results and other contributions of the Dynamics Explorer hot plasma and magnetic field measurements to the present understanding of magnetosphere-ionosphere coupling are reviewed in this paper.

Burch, J. L.↗