Engineering topics

Huang, C. Y.

Publications and source records attributed to Huang, C. Y..

At least 37 records · Page 2

NASA NTRS1989

Spectral characteristics of plasma sheet ion and electron populations during undisturbed geomagnetic conditions

The spectral characteristics of plasma-sheet ion and electron populations during periods of low geomagnetic activity were determined from the analysis of 127 one-hour average samples of central plasma sheet ions and electrons. Particle data from the ISEE-1 low-energy proton and electron differential energy analyzer and medium-energy particle instrument were combined to obtain differential energy spectra in the plasma sheet at geocentric radial distances above 12 earth radii. The relationships between the ion and electron spectral shapes and between the spectral shapes and the geomagnetic activity index were statistically investigated. It was found that the presence of interplanetary particle fluxes does not affect the plasma sheet particle spectral shape.

Christon, S. P.↗

NASA NTRS1989

Simultaneous observations of a theta aurora and associated magnetotail plasmas

Observations of a transpolar arc and simultaneous measurements of associated plasmas in the magnetotail lobe on March 25, 1982, are presented. The auroral imager on board Dynamics Explorer 1 observes a theta aurora in the northern polar cap for more than two hours, between 0502 and 0720 UT. ISEE 1 is located in the southern lobe of the geomagnetic tail at a distance of 22.2 R(E) during this time. The plasma and particle detectors measure intermittent bursts of particle fluxes between 0530 and 0705 UT. The observations suggest that these particle fluxes represent the high-altitude signature of a theta aurora in the southern polar cap. The relatively dense and energetic plasmas are organized into several filamentary structures. Magnetic mapping between the two polar regions indicates that the theta aurora in the Southern Hemisphere is a mirror reflection about the noon-midnight meridional plane of the theta aurora in the Northern Hemisphere.

Huang, C. Y.↗

NASA NTRS1989

Observational determination of the adiabatic index in the quiet time plasma sheet

An anticorrelation in the plasma density and temperature in the quiet time (AE of less than 100 nT) central plasma sheet has been demonstrated. The present results suggest that the adiabatic index is less than 1, and that earthward convecting plasma cools as it is compressed. It is pointed out that there are no observations which can presently account for the heat loss noted for the earthward convecting flux tubes of the central plasma sheet.

Huang, C. Y.↗

NASA NTRS1989

Three-dimensional simulation of whistler mode excited by the Spacelab 2 electron beam

During the Spacelab 2 mission, while an electron beam was being ejected from the Shuttle, the Plasma Diagnostics Package (PDP) detected a clear funnel-shaped emission that is believed to be caused by whistler-mode emission from the electron beam. In order to understand the mechanism of this emission, simulations with a three-dimensional partially magnetostatic code have been performed. The simulation results show that whistler-mode and lower hybrid waves are excited by the electron beam, which is initially localized in the column in the three-dimensional simulation system, and that they propagate away from the beam. The wave spectra of the electric and magnetic fields diagnosed at some points show several peaks due to the waves excited by the electron beam. The frequency range of these spectra is in qualitative agreement with the PDP data. The intense narrowband electrostatic emission near the electron plasma frequency is observed by the simulations. The simulation results show that the beam instability is responsible for the generation mechanism of these emissions.

Nishikawa, K.-I.↗

NASA NTRS1989

Processing of strong flux trapping high T(subc) oxide superconductors: Center director's discretionary fund

Magnetic suspension effect was first observed in samples of YBa2Cu3O7/AgO(Y-123/AgO) composites. Magnetization measurements of these samples show a much larger hysteresis which corresponds to a large critical current density. In addition to the Y-123AgO composites, recently similar suspension effects in other RE-123/AgO, where RE stands for rare-Earth elements, were also observed. Some samples exhibit even stronger flux pinning than that of the Y-123/AgO sample. An interesting observation was that in order to form the composite which exhibits strong flux trapping effect the sintering temperature depends on the particular RE-123 compound used. The paper presents the detailed processing conditions for the formation of these RE-123/AgO composites, as well as the magnetization and critical field data.

Wu, M. K.↗

NASA NTRS1988

Boundary layer dynamics in the description of magnetospheric substorms

This paper presents an analysis of eleven magnetospheric substorm events for which good-quality ground-based magnetometer data and ISEE satellite data were both available. It is shown that the magnetotail particle and field observations associated with a substorm expansive phase can be explained through the spatial movement of the boundary layers and central plasma sheet in the magnetotail. The sweeping of these regions past the satellite, even in the absence of temporal variations within the various regions, can lead to a set of plasma flow observations typical of what is observed in the magnetotail during substorm activity.

Eastman, T. E.↗

NASA NTRS1988

Observation of enhanced properties in samples of silver oxide doped YBa2Cu3O(x)

Samples of YBa2Cu3O(x) doped with silver oxide (Tc is about 93 K) have exhibited attractive forces in gradient magnetic fields, both normal and tangential to the surfaces, which are more than twice the sample weight. This allows sample suspension below a rare earth magnet. Critical current density was increased by about 100 at 77 K. Persistent fields, flux pinning, magnetization, and modeling are described.

Peters, P. N.↗

NASA NTRS1988

Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.

Nishikawa, K.-I.↗

NASA NTRS1988

Energy spectra of plasma sheet ions and electrons from about 50 eV/e to about 1 MeV during plamsa temperature transitions

ISEE-1 charged-particle measurements obtained during eight plasma temperature transitions (PTTs) in 1978-1979 are compiled in tables and graphs and analyzed in detail, comparing the ion and electron differential energy spectra with the predictions of theoretical models. PTTs are defined as approximately 1-h periods of low bulk plasma velocity and steadily increasing or decreasing thermal energy. A Maxwellian distribution is found to be inadequate in describing the PTT energy spectra, but velocity-exponential and kappa distributions are both successful, the latter especially at higher energies. The power-law index kappa varies from PTT to PTT, but the high-energy spectral index and overall shape of the distribution remain constant during a PTT; both spatial and temporal effects are observed.

Christon, S. P.↗

NASA NTRS1988

Magnetic properties of superconducting GdBa2Cu3O(6 + delta) at low temperature and high field

The magnetization of antiferromagnetic superconducting GdBa2Cu3O(6 + delta) has been measured for T in the range of 1.5 - 4.2 K for magnetic fields up to about 20 T. It is found that all Gd(3+) spins are nearly parallel at very high fields, and that this saturated spin subsystem coexists with superconductivity. Below the Neel temperature, 2.22 K, the transition from the 'canted' phase to the paramagnetic phase is observed by the application of a high magnetic field. The temperature dependence of this phase transition is also reported.

Huang, C. Y.↗

NASA NTRS1988

High-temperature processing of oxide superconductors and superconducting oxide-silver oxide composite

High temperature processing was found to partially convert the green 211 phase oxide to 123 phase. High Tc superconductivity was observed in Bi-Sr-Cu-O and Y-Sr-Cu-O systems prepared using the same heat treatment process. High temperature processing presents an alternative synthetic route in the search for new high Tc superconductors. An unusual magnetic suspension with enhancement in critical current density was observed in the 123 and AgO composite.

Wu, M. K.↗

NASA NTRS1987

Quadrennial review of the magnetotail

The findings of research conducted on the magnetotail in the years 1983-1986 are presented. The topics discussed include observations of the distant (between 60 and 220 earth radii) and the near-earth (earthward of 35 earth radii) magnetotail regions by the ISEE l, 2, and 3 and IMP 8 spacecraft, and magnetotail theory and modeling. These studies established the association between substorms and plasmoids in the deep tail and the linkage between the magnetosphere and the ionosphere via field-aligned currents and electric fields.

Huang, C. Y.↗

NASA NTRS1987

Filamentary structures in the magnetotail lobes

The observations of plasmas which may be the source population for polar cap arcs are reported. This population consists of energetic plasma contained within filamentary structures aligned approximately parallel to the XZ plane. Using a combination of plasma, particle, and magnetic field data for several events, it is established that the filaments have their origin in the plasma sheet or its adjacent boundary layer, and that the structures protrude into the lobe region. In a number of cases, a correlation between the convection pattern and the IMF B(Z) can be inferred. This is in agreement with the observed characteristics of polar cap arcs, observations of which are correlated with a northward directed IMF. The presence of field-aligned currents suggests that field-aligned acceleration may occur between the observing satellite and earth.

Huang, C. Y.↗

NASA NTRS1987

Observations of plasma distributions during the coordinated data analysis workshop substorms of March 31 to April 1, 1979

On March 31 and April 1, 1979, a sequence of substorms was recorded on the ground. During the entire active period the ISEE 1 and 2 satellites were located in the magnetotail, between 22 R(E) and 12 R(E) from the earth. Observations of plasma distributions made at varying levels of activity during these substorms provide good examples of typical magnetotail responses. While the entire magnetotail undergoes temporal variations during substorm activity, the most obvious effect seen is spatial motion of preexisting plasma regimes; for example, at substorm onset the central plasma sheet contracts. This can cause a spacecraft to move from the plasma sheet into the boundary layer. As the plasma sheet boundary layer almost always comprises streaming plasma, the high-speed flows observed there are not necessarily due to the substorm process. The essential nature of the main plasma regions of the magnetotail is relatively unchanged during high activity.

Huang, C. Y.↗

NASA NTRS1987

Magnetic studies of high Tc superconducting (La0.9Sr0.1)2CuO4-y

The magnetic moment of La(0.9Sr0.1)2CuO4-y was measured as a function of temperature and magnetic field, and the onset of superconductivity was found to occur at a temperature of 35 K. At 2 K, the dc magnetic susceptibility was found to reach 83 percent of perfect diamagnetism. Field studies have shown that the sample is a type-II superconductor and that the temperature dependences of the critical fiedls are anomalous. Its critical fields, kappa, and lambda(eff) are much larger than those for (La0.9Ba0.1)2CuO4-y, and their temperature dependences cannot be explained in terms of BCS theory.

Zirngiebl, E.↗

NASA NTRS1987

Upper critical field of high temperature Y(1.2)Ba(0.8)CuO(4-delta) superconductor

A 20-T high-field magnet is used to measure electrical resistance as a function of temperature in the Y(1.2)Ba(0.8)CuO(4-delta) superconductor. The temperature dependence of the critical field, Hc2(T), is obtained from the superconduction transition. A Hc2(O) value of 166T is determined which is the highest critical field yet reported. Results show Y(1.2)Ba(0.8)CuO(4-delta) to be a 90K Type-II superconductor, with a lower critical field Hc1(O) of about 0.2T and a penetration depth of about 290 A.

Hor, P. H.↗

NASA NTRS1987

Plasma flows near the neutral sheet of the magnetotail

The Lepedea on board ISEE 1 is used to investigate the bulk flow plasma in the neutral sheet region (defined as the area where BX approx = O) of the magnetotail. For the majority of crossings there is no appreciable change in the macroscopic plasma parameters, i.e., the density, temperature and velocity of the plasma remain constant through the neutral sheet. This is true even during active periods, when AE is somewhat greater than 100nT. However, for a small number of crossings, all during disturbed times, large plasma bulk velocities abs. val V is greater than or = 300 km/s are observed. The velocity distributions during these events are qualitatively similar to those of the plasma sheet boundary layer that is usually observed at higher latitudes. The acceleration mechanism which creates the plasma sheet boundary layer extends to relatively small radial distances during these active periods.

Huang, C. Y.↗

NASA NTRS1986

A statistical study of the central plasma sheet - Implications for substorm models

The University of Iowa Lepedea on board ISEE 1 is used to investigate the characteristics of the central plasma sheet under all levels of geomagnetic activity. Positive ion responses from 1 eV to 45 keV are used in this study. All the periods during 1978 when the central plasma sheet is encountered are included. This study excludes all boundary layer samples. The results of this study show that the central plasma sheet consists of plasma with high thermal energy (several keV) but low bulk speeds. This remains true even during high geomagnetic activity. The main effect of increasing activity is heating of the plasma sheet, preferentially at the high-latitude boundaries.

Huang, C. Y.↗