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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Effects of applied dc radial electric fields on particle transport in a bumpy torus plasma

The influence of applied dc radial electric fields on particle transport in a bumpy torus plasma is studied. The plasma, magnetic field, and ion heating mechanism are operated in steady state. Ion kinetic temperature is more than a factor of ten higher than electron temperature. The electric fields raise the ions to energies on the order of kilovolts and then point radially inward or outward. Plasma number density profiles are flat or triangular across the plasma diameter. It is suggested that the radial transport processes are nondiffusional and dominated by strong radial electric fields. These characteristics are caused by the absence of a second derivative in the density profile and the flat electron temperature profiles. If the electric field acting on the minor radius of the toroidal plasma points inward, plasma number density and confinement time are increased.

Roth, J. R.↗
NASA NTRS1973

Research in particles and fields in space

Theoretical and experimental work in charged particle and magnetic field research is reported. Activities center on plasma generation and acceleration, ATS 1 data processing for evaluation of magnetospheric substorms and micropulsations during magnetic disturbances, and the development of solar wind model using Mariner observations.

Coleman, P. J., Jr.↗
NASA NTRS1975

Particle and field environment of Uranus

In 1985 the spin axis of Uranus points within 10 degrees of the sun and the planet's position is very near the solar apex direction. A Uranus mission with an encounter near 1985 might expect to measure the unusual particle and field configuration of a 'pole-on' magnetosphere and also properties of the interstellar medium. Estimates are given of the particle and field environment of Uranus based on extrapolation of solar-wind data from 1 AU and on scaling relations for an earth-type magnetosphere. Since the magnetic moment of Uranus is unknown, all magnetospheric parameters are derived as a function of the dipole strength. The onsets of special magnetospheric properties are identified as the dipole moment increases from small to large values. A fairly complete set of magnetospheric parameters is given for a specific dipole moment to illustrate the case of a large moment.

Siscoe, G. L.↗
NASA NTRS1981

Particle and field measurements on two J-series 30 centimeter thrusters

Tests were performed to characterize the particles and fields associated with two 30 cm mercury ion thrusters operating independently and simultaneously. Flux rates and energies of ions and their distribution around the thrusters were determined. Facility effect ions were measured and their effect on thruster created flux measurements was assessed. The flux rate and distribution of sputtered metal atoms was determined and compared with theory and previous measurements. Mapping of the potential fields in the near vicinity of the thrusters was accomplished.

Lathem, W. C.↗
NASA NTRS1986

Cyclotron maser radiation from a source structure localized perpendicular to the ambient magnetic field

Particle simulations were used to investigate the properties of electromagnetic radiation produced by the cyclotron maser instability in a source region which is localized in the direction perpendicular to the uniform magnetic field. In the procedure used, the simulation model of Pritchett and Strangeway (1985) for the generation of auroral kilometric radiation (AKR) along an auroral field line was modified to include inhomogeneities perpendicular to the magnetic field. The results are compared with the previous homogeneous simulations with regard to efficiency and saturation mechanism and with expectations based on the feedback model. The implications for the generation and propagation of AKR are discussed.

Pritchett, P. L.↗
NASA NTRS1980

Dynamics of plasma, energetic particles, and fields near synchronous orbit in the nighttime sector during magnetospheric substorms

Two phases of substorm-associated magnetospheric dynamics are discussed in terms of particles and fields at synchronous orbit. The first phase corresponds to the 'decreases' of energetic particle flux. The second phase is the conventional expansion phase that begins with the 'onset', characterized in the study by (1) a sudden decrease in the tail current and a return of the inflated magnetosphere to a dipolelike configuration, (2) a sudden shift of trapped high-energy particles toward the tail again following contours of constant B, and at the same time (3) a surge of tail plasma toward the earth as the induced electric field now increases the total convection field.

Sauvaud, J.-A.↗
NASA NTRS1973

Particle and field payloads

The capability of the Space Shuttle for the conduct of magnetospheric experiments is critically analyzed. Some physical problems are discussed on which a particle and field payload program could be based. They include the study of magnetospheric plasma processes, wave-particle interactions and auroral phenomena, both by artificial modification experiments and by systematic wide-scale observations of naturally occurring magnetospheric perturbation events.

Roederer, J. G.↗
NASA NTRS1981

Particle and field measurements on two J-series 30-centimeter thrusters

An experimental investigation under complete computer control of the characteristics of particles and fields emanating from mercury bombardment ion thrusters (J-series, 30 cm diameter), operating independently and simultaneously, is discussed. Results show that the flux rate of sputtered metal atoms leaving a single thruster has been determined and the data is in agreement with previous test results. The flux rate and energies of ions leaving single and two-thruster configurations have been established for a variety of beam current levels and combinations involving the two thrusters, and the data are sufficient to establish upper bounds. Floating potential measurements made in the near vicinity of the thrusters indicate that the fields are weak, plus or minus a few volts. The tests may be significant for the Solar Electric Propulsion System (SEPS) planners.

Lathem, W. C.↗
NASA NTRS1992

Distribution of particles and fields in turbulent media

It is shown that fluctuations of kinetic coefficients can lead to the development of an instability that tends to increase the gradients of the distribution of particles and fields in turbulent media. It is found that high rank correlation functions of the cosmic medium turbulent velocity must be taken into account in most real cases. Turbulence in compressible media can lead to a decrease of the CR diffusion coefficient. In some cases the diffusion coefficient may become negative, which implies the development of an instability with respect to the formation of clusters of particles. A similar instability may exist for fields in turbulent media and in media with fluctuation parameters. It may lead to the bunching of magnetic field lines and to the fractal structure of waves propagating in the media.

Dolginov, A. Z.↗
NASA NTRS1988

Electric fields and particle precipitation during the substorm of January 18, 1984

The transition between the quiet and active conditions in the early afternoon high-latitude ionosphere is examined. Particular attention is given to the electric field and particle precipitation response to a slow monotonic decrease in the interplanetary magetic field Bz component. Observations from the Sondrestrom incoherent-scatter radar and the NOAA 7 satellite are analyzed. The electric field is found to intensify very quickly after the change in Bz.

De La Beaujardiere, O.↗
NASA NTRS1980

Research in particles and fields

The astrophysical aspects of cosmic and gamma rays and the radiation environment of the Earth and other planets investigated by means of energetic particle detector systems flown on spacecraft and balloons are discussed. The theory of particles and fields in space is also addressed with particular emphasis on models of Saturn's magnetic field.

Vogt, R. E.↗
NASA NTRS1992

Particles and fields measurements at Neptune with Voyager 2

The first results of measurements performed on the Voyager 2 spacecraft with the Neptune system on August 24-28, 1989 are summarized. These include measurements of the magnetic field, plasma, energetic and high energy particles, plasma waves and radio emissions, and additional information relating to UV emissions. The planetary magnetic field outside about 4 R(N) may be described by an offset, tilted, dipole of moment 0.133 Gauss-R(N) exp 3; inside that distance the field is dominated by higher order terms. Plasma densities are found to be generally low (about 5 exp -3/cu cm), except at magnetic equatorial crossings when densities are up to about 1/cu cm. A variety of plasma wave emissions were seen, including chorus, hiss, electroncyclotron waves, and upper hybrid resonance in the inner magnetosphere. The measured flux of soft electrons and ions over the polar region of about 2 x 10 exp -3 erg/sq cm sec results in an estimated power input of about 3 x 10 exp 7 W, which is substantially less than that at other planets.

Krimigis, S. M.↗
NASA NTRS2021

Simultaneous UV Images and High-Latitude Particle and Field Measurements During an Auroral Dawn Storm at Jupiter

We present multi-instrument Juno observations on day-of-year 86, 2017 that link particles and fields in Jupiter's polar magnetosphere to transient UV emissions in Jupiter's northern auroral region known as dawn storms. Juno ranged from 42°N to 51°N in magnetic latitude and 5.8–7.8 Jovian radii (1 RJ = 71,492 km) during this period. These dawn storm emissions consisted of two separate, elongated structures which extended into the nightside, rotated with the planet, had enhanced brightness (up to at least 1.4 megaRayleigh) and high color ratios. The color ratio is a proxy for the atmospheric penetration depth and therefore the energy of the electrons that produce the UV emissions. Juno observed electrons and ions on magnetic field lines mapping to these emissions. The electrons were primarily field-aligned, bidirectional, and, at times, exhibited sudden intensity decreases below ∼10 keV coincident with intensity enhancements up to energies of ∼1,000 keV, consistent with the high color ratio observations. The more energetic electron distributions had characteristic energies of ∼160–280 keV and downward energy fluxes (∼70–135 mW m−2) that were a significant fraction needed to produce the UV emissions for this event. Magnetic field perturbations up to ∼0.7% of the local magnetic field showing evidence of upward and downward field-aligned currents, whistler mode waves, and broadband kilometric radio emissions were also observed along Juno's trajectory during this time frame. These high-latitude observations show similarities to those in the equatorial magnetosphere associated with dynamics processes such as interchange events, plasma injections, and/or tail reconnection.

R. W. Ebert↗
NASA NTRS1971

Field-aligned particle currents near an auroral arc.

A Nike-Tomahawk rocket equipped to measure electric and magnetic fields and charged particles from a few eV to several hundred keV energy was flown into an auroral band on April 11, 1970. The purpose of this flight was to obtain evidence of the low-energy electrons and protons that constitute a field-aligned sheet current, and also to obtain the magnetic signature of such a current and the electric field in and near the auroral-arc electric current system. Particular attention was given to a sudden increase in the field-aligned current associated with a prior sudden increase in the electric field and a sudden change in the magnetic field, all occurring near the edge of a visual auroral arc. Data obtained are discussed and analyzed; they present an important contribution to the problem of mapping of atmospheric auroral phenomena to the magnetospheric equatorial plane.

Choy, L. W.↗