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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Three-dimensional interplanetary stream magnetism and energetic particle motion

Cosmic rays interact with mesoscale configurations of the interplanetary magnetic field. A technique is presented for calculating such configurations in the inner solar system, which are due to streams and source conditions near the sun, and maps of magnetic field are constructed for some plausible stream and source conditions. One effect of these mesoscale configurations on galactic cosmic rays is shown to be an out-of-the-ecliptic gradient drift sufficient to explain Forbush decreases. The effects on solar energetic particles include small polar drifts due to the field gradients and a possibly large modification of the time-intensity profiles and anisotropy characteristics due to the formation of mirror configurations in space. If a diffusion model is applicable to solar particles, the true diffusion coefficient will be masked by the effects of streams. A conceptual model which incorporates these ideas and those of several other models is presented.

Barouch, E.↗
NASA NTRS1969

Cryogenic flux-concentrator

Flux concentrator has high primary to secondary coupling efficiency enabling it to produce high magnetic fields. The device provides versatility in pulse duration, magnetic field strengths and power sources.

Bailey, B. M.↗
NASA NTRS1975

Thermospheric composition

The global view of the atmosphere provided by satellite observations and radar backscatter measurements has shown a pattern of composition variability resulting largely from dynamic processes. Important progress has been made in defining composition variability at 120 km, which has greatly improved models which previously had fixed boundary conditions at that altitude. The discovery of the early morning maximum in helium abundance and the better definition of diurnal variation in relative composition have provided a basis for more sophisticated dynamical models. Similarly, models of meridional wind systems have been developed which can account for the better-defined winter enhancements in helium and atomic oxygen. Finally, composition variability has indicated the presence of a high-latitude heat source which during periods of magnetic activity profoundly modifies the state of the atmosphere.

Carignan, G. R.↗
NASA NTRS1979

Dissociative and double photoionization of CO2 from threshold to 90 A

The molecular photoionization, dissociative photoionization and double photoionization cross sections for CO2 were measured from their onsets down to 90 A by using various combinations of mass spectrometers (a coincidence time-of-flight mass spectrometer and a magnetic mass spectrometer) and light sources (synchrotron radiation, and glow and spark discharge). It is concluded that the one broad peak and the three shoulders in the total adsorption cross section curve between 640 and 90 A are caused completely by dissociative ionization processes. Several peaks observed in the cross section curve for the total fragmentation CO(+)3, O(+) and C(+) are compared with those in the photoelectron spectrum reported for CO2.

Masuoka, T.↗
NASA NTRS1979

Induced electric currents in the Alaska oil pipeline measured by gradient, fluxgate, and SQUID magnetometers

The field gradient method for observing the electric currents in the Alaska pipeline provided consistent values for both the fluxgate and SQUID method of observation. These currents were linearly related to the regularly measured electric and magnetic field changes. Determinations of pipeline current were consistent with values obtained by a direct connection, current shunt technique at a pipeline site about 9.6 km away. The gradient method has the distinct advantage of portability and buried- pipe capability. Field gradients due to the pipe magnetization, geological features, or ionospheric source currents do not seem to contribute a measurable error to such pipe current determination. The SQUID gradiometer is inherently sensitive enough to detect very small currents in a linear conductor at 10 meters, or conversely, to detect small currents of one amphere or more at relatively great distances. It is fairly straightforward to achieve imbalance less than one part in ten thousand, and with extreme care, one part in one million or better.

Campbell, W. H.↗
NASA NTRS1980

Mass ejections

Observations and model simulations of solar mass ejection phenomena are examined in an investigation of flare processes. Consideration is given to Skylab and other observations of flare-associated sprays, eruptive prominences, surges and coronal transients, and to MHD, gas dynamic and magnetic loop models developed to account for them. Magnetic forces are found to confine spray material, which originates in preexisting active-region filaments, within steadily expanding loops, while surges follow unmoving, preexisting magnetic field lines. Simulations of effects of a sudden pressure pulse at the bottom of the corona are found to exhibit many characteristics of coronal transients associated with flares, and impulsive heating low in the chromosphere is found to be able to account for surges. The importance of the magnetic field as the ultimate source of energy which drives eruptive phenomena as well as flares is pointed out.

Rust, D. M.↗
NASA NTRS1981

The Solar Optical Telescope /SOT/

The Solar Optical Telescope (SOT) is a 1-m class, high resolution solar telescope which NASA plans to operate on the Shuttle Spacelab during the mid and late 1980's. SOT will provide resolution down to 0.1 arcsec, and can therefore be used to solve many problems of solar atmosphere structure and dynamics. In particular, SOT should provide definite data on (1) the source of the sun's magnetic field, (2) the amount of power in waves generated in the photosphere, (3) the heating of the chromosphere, and (4) the local and global mass and energy balance in the solar transition region. The SOT Scientific Working Group will help plan, develop, and update the overall scientific plan for the SOT, as well as make recommendations with regard to the SOT project, instrumentation optimization, and scientific data management.

Jordan, S. D.↗
NASA NTRS1982

The dynamic response of the thermosphere to the energy influx resulting from energetic O/+/ ions

Precipitating fluxes of energetic O(+) ions during magnetic storms constitute a significant source of energy to the nightside thermosphere at altitudes above 200 km. The resulting perturbations of temperature and winds in the thermosphere due to energetic O(+) precipitation are examined by computing the heating rate profile from such a precipitation event and using this as input to the NCAR thermospheric general circulation model. The results of a time dependent calculation show that heating due to energetic O(+) ion precipitation produces a significant perturbation to the thermospheric structure above about 300 km. Energetic O(+) precipitation events should produce considerable variability in the upper thermosphere during geomagnetic storms.

Torr, M. R.↗
NASA NTRS1984

Generation of broadband electrostatic noise by ion beam instabilities in the magnetotail

Particle data from ISEE 1 sampled in the earth's magnetotail show the presence of energetic ion beams in the boundary layer of the plasma sheet. A theory of instabilities driven by the beams is developed and compared with wave data sampled simultaneously to the particle data. It is concluded that the ion beams generate broadband electrostatic bursts of noise. The electrostatic noise correlates well with the occurrence of the beams, and the spectrum is consistent with that predicted from a negative energy beam instability under magnetotail conditions. The theory predicts that a spectrum of growing waves can be driven for frequencies from 0.001 omega(pe) up to omega(pe), the electron plasma frequency, with a spectral peak typically near 0.01 omega(pe) or lower, in agreement with the wave data. Furthermore, as one moves away from the source region perpendicular to the magnetic field, the high frequency components of the observed wave spectra are predicted to disappear gradually, leaving the low frequency part of the spectrum, also as is observed. Evidence is given for significant pitch angle scattering of the beams by the broadband electrostatic noise, leading to more isotropic ion distributions.

Grabbe, C. L.↗
NASA NTRS1985

Laboratory measurement of the P(2,1) submillimeter transition frequency of H3O(+)

The molecular ion H3O(+) is predicted to be an important component of the gas phase of interstellar clouds where it is calculated to be one of the most abundant molecular ions. Its detection would provide an indirect method of determining the abundance of the crucial species H2O. This fundamental molecule has no convenient low-lying transitions in the microwave or millimeter regions of the spectrum which can be excited under the normal low temperature conditions present in the interstellar medium. It is believed that the P(2,1) transition of H3O(+) in absorption at a frequency of 307 192.41 (5) MHz has been detected. The H3O(+) ion was produced in a magnetically enhanced negative glow discharge source.

Plummer, G. M.↗
NASA NTRS1985

Electromagnetic ion beam instabilities. II

The results of Gary et al. (1984) on the properties of the right-hand resonant and nonresonant electromagnetic ion beam instabilities for relatively cool beam temperatures are extended. In particular, the parametric dependence of the real frequency at maximum growth of these modes is examined. It is demonstrated that the right-hand resonant ion beam instability can have maximum growth at frequencies near the ion-cyclotron frequency if the beam main component relative drift speed is about twice the Alfven speed and at least one of two conditions holds: that the ion beta or the beam main component relative temperature are sufficiently small, or the perpendicular-to-parallel beam temperature ratio is sufficiently large. These results support the identification of the right-hand resonant instability as the source of the large amplitude magnetic fluctuations observed upstream of slow shocks in the earth's magnetotail.

Gary, S. P.↗
NASA NTRS1986

A study of hard X-ray associated meter-decameter bursts observed on December 19, 1979

The results of a study of the relationship of a complex meter-decameter wavelength radio burst observed with the Clark Lake E-W and N-S interferometers, with a hard X-ray burst observed with the X-ray spectrometer aboard ISEE-3 are presented. The radio burst consisted of several type III's, reverse drift type III's, a U burst, and type II and type IV bursts. The X-ray emission was also complex. The radio as well as hard X-ray emissions were observed before the flash phase of the flare; they were not always associated and it is conjectured that this may constitute evidence for acceleration of electrons high in the corona. On the other hand, all components of the reverse drift burst were associated with hard X-ray subpeaks, indicating multiple injection of electron beams along field lines with different density gradients. While the type II burst appeared to be related to the hard X-ray burst, a detailed correspondence between individual features of the radio and hard X-ray burst emissions could not be found. The type IV burst started after all hard X-ray emissions ceased. Its source appeared to be a magnetic arch, presumably containing energetic electrons reponsible for the gyrosynchrotron radiation of type IV.

Kundu, M. R.↗
NASA NTRS1986

The role of narrowband dm-spikes in solar flares

The main observational characteristics of narrowband dm-spikes are summarized. Since the spikes are observed in typical sequences of radio bursts, a global model of these bursts is presented. The intensity of the magnetic field in the spike source region, which is of principal importance, is discussed.

Karlicky, Marian↗
NASA NTRS1986

The sun and the heliosphere in three dimensions; Proceedings of the Nineteenth ESLAB Symposium, Les Diablerets, Switzerland, June 4-6, 1985

Papers are presented on coronal magnetic fields, the heliospheric energy source, stereoscopic measurement of hard solar X-rays, and OVI diagnostics of solar-wind generation. Also considered are coronal transients at high heliospheric latitudes, the solar-cycle dependence of coronal mass ejections, comets and three-dimensional wind structure, and interplanetary scintillation observations of the solar wind at high latitudes. Other topics include three-dimensional coronal and heliospheric structure from radio observations, multispacecraft observations of Type III radio bursts, the acceleration of energetic particles at solar-wind shocks, and a spatially confined, long-lived stream of solar particles.

Marsden, R. G.↗
NASA NTRS1987

30-cm electron cyclotron plasma generator

Experimental results on the development of a 30-cm-diam electron cyclotron resonance plasma generator are presented. This plasma source utilizes samarium-cobalt magnets and microwave power at a frequency of 4.9 GHz to produce a uniform plasma with densities of up to 3 x 10 to the 11th/cu cm in a continuous fashion. The plasma generator contains no internal structures, and is thus inherently simple in construction and operation and inherently durable. The generator was operated with two different magnetic geometries. One used the rare-earth magnets arranged in an axial line cusp configuration, which directly showed plasma production taking place near the walls of the generator where the electron temperature was highest but with the plasma density peaking in the central low B-field regions. The second configuration had magnets arranged to form azimuthal line cusps with approximately closed electron drift surfaces; this configuration showed an improved electrical efficiency of about 135 eV/ion.

Goede, Hank↗
NASA NTRS1988

Accretion-driven nonthermal phenomena

Arguments are presented which suggest that accretion disks around black holes and neutron stars may self-generate ordered magnetic fields, from currents associated with orbital motion of the disk material. This leads one to expect electromagnetic extraction of the rotational energy of the disk, and it is proposed that such a magnetic field is the ultimate source of various nonthermal phenomena in accreting ultracompact objects.

Walker, Mark↗