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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Earthward transport of energetic protons in the earth's plasma sheet

An analysis is made to assess the transport of energetic protons (0.29-0.50 MeV) at downstream distances of 30-45 earth radii in the earth's plasma sheet surveyed by the IMP 7 and IMP 8 spacecraft. It is found that there is a net earthward transport of these particles, although tailward streaming is observed as frequently as earthward streaming. The averaged flux is 200 per sq cm s in this energy range and the total flux over the plasma sheet region is 4 x 10 to the 22nd per s. It is suggested that this net earthward flux of energetic protons may contribute to the population of the outer radiation belt.

Lui, A. T. Y.↗
NASA NTRS1982

System for slicing wafers

A newly patented process for slicing silicon wafers that has distinct advantages over methods now widely used is described. The primary advantage of the new system is that it allows the efficient slicing of a number of ingots simultaneously at high speed. The cutting action is performed mechanically, most often with diamond particles that are transported to the cutting zone by a fluid vehicle or have been made an integral part of the blade by plating or impregnation. The new system uses a multiple or ganged band saw, arranged and spaced so that each side, or length, segment of a blade element, or loop, provides a cutting function. Each blade is maintained precisely in position by guides as it enters and leaves each ingot. The cutting action is performed with a conventional abrasive slurry composed of diamond grit suspended in an oil- or water-based vehicle. The distribution system draws the slurry from the supply reservoir and pumps it to the injection tubes to supply it to each side of each ingot. A flush system is provided at the outer end of the work-station zone. In order to reduce potential damage, a pneumatically driven flushing fluid is provided.

Source record↗
NASA NTRS1985

Solar and interplanetary particles at 2 to 4 MEV during solar cycles 21, solar cycle variations of event sizes, and compositions

In This paper 2 to 4 MeV/nucleon protons, alpha particles, and medium (CNO) nuclei in the near-Earth interplanetary medium during the years 1974 to 1981 are studied. This period contains both the solar activity minimum in 1976, and the very active onset phase of Solar Cycle 21. Characteristic compositional differences between the solar minimum and solar maximum ion populations have been investigated. Previous studies of interplanetary composition at these energies have concentrated on well-defined samples of the heliospheric medium. During flare particle events, the ambient plasma is dominated by ions accelerated in specific regions of the solar atmosphere; observation of the proton/alpha and alpha/medium ratios for flare events shows that there is marked compositional variability both during an event and from event to event suggesting the complicated nature of flare particle production and transport.

Armstrong, T. P.↗
NASA NTRS1986

Thermal catastrophe in the plasma sheet boundary layer

This letter presents a first step towards a substorm model including particle heating and transport in the plasma sheet boundary layer (PSBL). The heating mechanism discussed is resonant absorption of Alfven waves. For some assumed MHD perturbation incident from the tail lobes onto the plasma sheet, the local heating rate in the PSBL has the form of a resonance function of the one-fluid plasma temperature. Balancing the local heating by convective transport of the heated plasma toward the central plasma sheet, an 'equation of state" is found for the steady-state PSBL whose solution has the form of a mathematical catastrophe: at a critical value of a parameter containing the incident power flux, the local density, and the convection velocity, the equilibrium temperature jumps discontinuously. Associating this temperature increase with the abrupt onset of the substorm expansion phase, the catastrophe model indicates at least three ways in which the onset may be triggered. Several other consequences related to substorm dynamics are suggested by the simple catastrophe model.

Smith, Robert A.↗
NASA NTRS1989

Report from space plasma science

Space plasma science, especially plasma experiments in space, is discussed. Computational simulations, wave generation and propagation, wave-particle interactions, charged particle acceleration, particle-particle interactions, radiation transport in dense plasmas, macroscopic plasma flow, plasma-magnetic field interactions, plasma-surface interactions, prospects for near-term plasma science experiments in space and three-dimensional plasma experiments are among the topics discussed.

Hastings, D. E.↗
NASA NTRS1990

Cosmic-ray streaming in the Born approximation

The present work invokes the Born approximation to derive a more accurate expression for the streaming of cosmic rays parallel to the mean magnetic field. While all prior results pertaining to the helicity dependence of the diffusion coefficient and convection speed can be recovered as special cases from this streaming equation, it is concluded that a new set of transport parameters presented here is more appropriate for the solar modulation of galactic cosmic rays. In addition, a new parameter related to time variability, which may be a dominant cause of charge sign-dependent transport of solar particles, is introduced.

Bieber, J. W.↗
NASA NTRS1990

The generalized diffusion-convection equation

Starting from the Boltzmann equation, a transport equation is derived for energetic particles in a moving magnetized plasma in which the scattering centers that keep the particles quasi-isotropic are moving with a velocity that is not necessarily the same as that of the plasma. The scattering is characterized by three very loose constraints: (1) there is a rest frame for each scatterer in which the particles scatter elastically; (2) in this frame the scattering will not disturb an isotropic distribution; and (3) the momentum transfer in an average collision may be described by a tensor operating on the particles original momentum. Since the strength of the scattering is not specified, the derivation should be as valid for plasma microturbulence as for hard-sphere scattering. The results show clearly which phenomena are responsible for tying the particles to the plasma in the transport equation.

Jones, Frank C.↗
NASA NTRS1990

A numerical study of the outflow layer of tropical cyclones

Numerical simulations of idealized tropical cyclones with special emphasis on the outflow layer are presented. The quasi-steady state outflow layers of weak and strong cyclones are found to exhibit similar characteristics. The circulations are anticyclonic and asymmetric about the center; the outflow layer is dominated by a narrow, elongated outflow-jet contributing up to 50 percent of the angular momentum transport; the air particles in the outflow jet mostly originate from the lower level. Secondary circulations are found to influence the relative humidity and the potential vorticity at the outflow levels. In order to study the effect of upper tropospheric forcings, two variational numerical experiments using cumulus convection as the major link between the upper-level forcing and the tropical cyclone's response are conducted.

Shi, Jainn-Jong↗
NASA NTRS1990

The Solar Probe mission

The Solar Probe will deliver a 133.5 kg science payload into a 4 R(S) perihelion solar polar orbit to explore in situ one of the last frontiers in the solar system - the solar corona. Using a payload of 12 scientific experiments, it will be possible to answer many long-standing fundamental problems concerning the structure and dynamics of the outer solar atmosphere, including the acceleration, storage, and transport of energetic particles near the sun and in the inner heliosphere.

Anderson, J.↗
NASA NTRS1990

The Mercury Dual Orbiter mission

The Mercury Orbiter (MeO) will carry out a full range of particles, fields, and planetary imaging science at Mercury. Present mission plans call for a launch in 1999 with a flight time of about 4.5 years. By means of multiple Venus and Mercury gravitational assists, the mission can be accomplished with present U.S. launch vehicles and a very large payload can be placed in orbit around Mercury. The dual-spacecraft concept will permit outstanding scientific study of solar cosmic rays and the solar wind throughout the inner heliosphere from 0.3 AU to 1.0 AU. Modest enhancements to the planned magnetospheric instruments and utilization of onboard solar instruments will permit unique investigation of solar particle acceleration and transport with the MeO spacecraft.

Baker, D. N.↗
NASA NTRS1992

Study of SMM flares in gamma-rays and neutrons

This report summarizes the results of the research supported by NASA grant NAGW-2755 and lists the papers and publications produced through the grant. The objective of the work was to study solar flares that produced observable signals from high-energy (greater than 10 MeV) gamma-rays and neutrons in the Solar Maximum Mission (SMM) Gamma-Ray Spectrometer (GRS). In 3 of 4 flares that had been studied previously, most of the neutrons and neutral pions appear to have been produced after the 'main' impulsive phase as determined from hard x-rays and gamma-rays. We, therefore, proposed to analyze the timing of the high-energy radiation, and its implications for the acceleration, trapping, and transport of flare particles. It was equally important to characterize the spectral shapes of the interacting energetic electrons and protons - another key factor in constraining possible particle acceleration mechanisms. In section 2.0, we discuss the goals of the research. In section 3.0, we summarize the results of the research. In section 4.0, we list the papers and publications produced under the grant. Preprints or reprints of the publications are attached as appendices.

Dunphy, Philip P.↗
NASA NTRS1994

Dynamics explorer interdisciplinary scientist investigations

This document is a final report on research activities and accomplishments that occurred during the funding period of 10-1-90 through 1-30-94. The focus of our interdisciplinary investigation during the Dynamics Explorer Mission was on the complex coupling processes that tap the magnetic-storm energy, stored in the ring current particle reservoir, and transport this energy into the subauroral, midlatitude and even equatorial ionospheric regions. The transport of energy through the inner magnetosphere and into the underlying ionospheric regions is a critical element in our understanding of the impact of solar and magnetic disturbances on upper atmospheric and ionospheric regions equatorward of the auroral zone.

Kozyra, Janet U.↗
NASA NTRS1994

Counting Particles Emitted by Stratospheric Aircraft and Measuring Size of Particles Emitted by Stratospheric Aircraft

There were two principal objectives of the cooperative agreement between NASA and the University of Denver. The first goal was to modify the design of the ER-2 condensation nuclei counter (CNC) so that the effective lower detection limit would be improved at high altitudes. This improvement was sought because, in the instrument used prior to 1993, diffusion losses prevented the smallest detectable particles from reaching the detection volume of the instrument during operation at low pressure. Therefore, in spite of the sensor's ability to detect particles as small as 0.008 microns in diameter, many of these particles were lost in transport to the sensing region and were not counted. Most of the particles emitted by aircraft are smaller than 0.1 micron in diameter. At the start date of this work, May 1990, continuous sizing techniques available on the ER-2 were only capable of detecting particles larger than 0.17 micron. Thus, the second objective of this work was to evaluate candidate sizing techniques in an effort to gain additional information concerning the size of particles emitted by aircraft.

Wilson, James Charles↗
NASA NTRS1997

Relative to the Caltech Electron/Isotope Spectrometer-IMP

The Electron Isotope Spectrometers (EIS) on IMP-8 was designed to provide measurements of low energy isotopes from H to O (1 less than or equal to Z less than or equal to 8) over the energy range from approx. 2 to approx. 40 MeV/nuc, as well as low energy electrons from approx. 0.2 to approx. 6 MeV. These measurements supported studies of the acceleration and transport of energetic particles originating on the Sun, in interplanetary space, in the Galaxy, and in Earth's and Jupiter's magnetosphere. IMP-8 was launched in October 1973 and still continues to provide key particles and fields measurements from orbit about the Earth. The IMP-8 EIS continued to operate flawlessly until 8/3/92, when a partial failure was suffered in a bias supply, which reduced the ability of the instrument to measure high energy particles. The EIS was subsequently turned off in 1995. A nearly identical instrument was flown on IMP-7 from 10/92 to 7/96, and many studies combined results from both instruments. For completeness, this report summarizes scientific results and publications from the entire IMP-7&8 effort, not just from the period covered by NAG5-727.

Source record↗
NASA NTRS2000

Delta 2 Explosion Plume Analysis Report

A Delta II rocket exploded seconds after liftoff from Cape Canaveral Air Force Station (CCAFS) on 17 January 1997. The cloud produced by the explosion provided an opportunity to evaluate the models which are used to track potentially toxic dispersing plumes and clouds at CCAFS. The primary goal of this project was to conduct a case study of the dispersing cloud and the models used to predict the dispersion resulting from the explosion. The case study was conducted by comparing mesoscale and dispersion model results with available meteorological and plume observations. This study was funded by KSC under Applied Meteorology Unit (AMU) option hours. The models used in the study are part of the Eastern Range Dispersion Assessment System (ERDAS) and include the Regional Atmospheric Modeling System (RAMS), HYbrid Particle And Concentration Transport (HYPACT), and Rocket Exhaust Effluent Dispersion Model (REEDM). The primary observations used for explosion cloud verification of the study were from the National Weather Service's Weather Surveillance Radar 1988-Doppler (WSR-88D). Radar reflectivity measurements of the resulting cloud provided good estimates of the location and dimensions of the cloud over a four-hour period after the explosion. The results indicated that RAMS and HYPACT models performed reasonably well. Future upgrades to ERDAS are recommended.

Evans, Randolph J.↗
NASA NTRS2001

Dayside Aurora Dynamics

Images from the FUV (Far UltraViolet) instrument on board the IMAGE spacecraft will be presented to demonstrate the auroral dynamics in the dayside auroral zone and the polar cap region. optical emissions detected by three different detectors of FUV come from precipitations of energetic protons, electrons, and both species, respectively. In general, auroral activities in these regions responded very well to variations in the boundary conditions either external or internal to the magnetosphere, i.e., in the solar wind or the magnetotail. As a result, auroral images from FUV provide an excellent tool to investigate particle acceleration and transport processes within the geospace, such as shock acceleration, substorm injections, etc. we will interpret the observed auroral images using various models, discuss difference and similarity in the auroral activity from several typical cases, and assess conditions optimal to each type of auroral activity.

Spann, James F.↗
NASA NTRS2003

Radiation Shielding for Space Flight

A safe and efficient exploration of space requires an understanding of space radiations so that human life and sensitive equipment can be protected. On the way to these sensitive sites, the radiation is modified in both quality and quantity. Many of these modifications are thought to be due to the production of pions and muons in the interactions between the radiation and intervening matter. A method to predict the effects of the presence of these particles on the transport of radiation through materials is presented.

Blattnig, Steve R.↗
NASA NTRS2004

Dust Transport and Deposition Observed from the Terra-MODIS Space Observations

Meteorological observations, in situ data and satellite images of dust episodes were used already in the 1970s to estimate that 100 tg of dust are transported from Africa over the Atlantic Ocean every year between June and August and deposited in the Atlantic Ocean and the Americas. Desert dust is a main source of nutrients to oceanic biota and the Amazon forest, but deteriorates air quality and caries pathogens as shown for Florida. Dust affects the Earth radiation budget, thus participating in climate change and feedback mechanisms. There is an urgent need for new tools for quantitative evaluation of the dust distribution, transport and deposition. The Terra spacecraft launched at the dawn of the last millennium provides first systematic well calibrated multispectral measurements from the MODIS instrument, for daily global analysis of aerosol. MODIS data are used here to distinguish dust from smoke and maritime aerosols and evaluate the African dust column concentration, transport and deposition. We found that 230+/-80 tg of dust are transported annually from Africa to the Atlantic Ocean, 30 tg return to Africa and Europe, 70 tg reach the Caribbean, 45 tg fertilize the Amazon Basin, 4 times as previous estimates thus explaining a paradox regarding the source of nutrition to the Amazon forest, and 120+/-40 tg are deposited in the Atlantic Ocean. The results are compared favorably with dust transport models for particle radius less than or equal to 12 microns. This study is a first example of quantitative use of MODIS aerosol for a geophysical study.

Kaufman, Y. J.↗