Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “events”

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 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Simulation of January 1-7, 1978 events

The solar wind disturbances of January 1 to 7, 1978 are reconstructed by a modeling method. First, the interplanetary magnetic field (IMF) background pattern, including a corotating shock, is reproduced using the Stanford source surface map. Then, two solar flares with their onset times on January 1, 0717 UT at S17 deg E10 deg and 2147 UT S17 deg E32 deg, respectively, are selected to generate two interplanetary transient shocks. It is shown that these two shocks interacted with the corotating shock, resulting in a series of interplanetary events observed by four spacecraft, Helios 1 and 2, IMP-8 (Interplanetary Monitoring Platform 8), and Voyager 2. Results show that these three shock wave interact and coalesce in interplanetary space such that Helios 2 and Voyager 2 observed only one shock and Helios 1 and IMP-8 observed two shocks. All shocks observed by the four spacecraft, except the corotating shock at Helios 1, are either a transient shock or a shock which is formed from coalescing of the transient shocks with the corotating shock. The method is useful in reconstructing a very complicated chain of interplanetary events observed by a number of spacecraft.

Chao, J. K.↗
NASA NTRS1987

Simultaneous measurements of energetic ion (50 keV and above) and electron (220 keV and above) activity upstream of earth's bow shock and inside the plasma sheet - Magnetospheric source for the November 3 and December 3, 1977 upstream events

Simultaneous observations of energetic ions and electrons by the IMP 7 and 8 spacecraft are used here to separate temporal variations from spatial variations during the upstream ion events observed on December 3, 1977 and November 2-3, 1977, in order to determine the source of these particles. Analysis of the observations and comparison with theory shows that: (1) for each of the observed upstream enhancements, energetic ions and electrons were simultaneously present inside the plasma sheet; (2) the low-energy ion intensity profile inside the plasma sheet was relatively flat, while at higher energies there was considrable variability; (3) relativistic electron bursts were seen inside the plasma sheet and also upstream of the shock but at substantially reduced intensities; (4) the ion energy spectrum for the December 3 event, extended to energies of about 2 MeV, was identical in form with the plasma sheet and upstream of the shock; (5) ion anisotropies exhibited typically large dawn-dusk or dusk-dawn gradients and large field-aligned streaming away from the bow shock.

Sarris, E. T.↗
NASA NTRS1987

Circumstances for Pluto-Charon mutual events in 1988

Physical parameters are tabulated for 89 Pluto-Charon mutual events occurring during the 1988 opposition. A primary star and a check star have been selected as comparison stars for events occurring prior to the 1988 opposition. Standardization of the comparison star 1987 Primary has provided a B magnitude of 12.3093 + or - 0.0013 and a V magnitude of 11.4215 + or - 0.0013. The designations, positions, and preliminary magnitudes and colors are also given for two transformation stars selected in order to aid in determination of the color terms necessary to convert the instrumental magnitudes of observers to the standard system.

Tholen, David J.↗
NASA NTRS1987

Interplanetary proton (Ep = 0.61-3.41 MeV) events observed with Pioneer 11, 1973-1986 and out to 22.4 AU

A survey of interplanetary proton (Ep = 0.61-3.41 MeV) events is summarized in graphical and tabular form for the period April 1973 - December 1986. The observations were obtained by an effectively continuous data stream from the University of Iowa instrument on the NASA Ames spacecraft Pioneer 11 as it moved outward in the solar system from 1.0 to 22.4 AU. A total of 265 distinct events are identified. The spectra and intensities of the protons, presumed to be originally of solar origin, are influenced dramatically by propagative and accelerative processes in the interplanetary medium.

Van Allen, James A.↗
NASA NTRS1988

Temperature dependence of the abundances of elements in solar He-3 rich events

The element abundances in solar He-3-rich events are observed to vary with the soft X-ray temperature of the parent flare. The observations are consistent with thermal collisional ionization of the elements to the equilibrium-charge states expected within the flare-heated plasma at (10-15) x 10 to the 6th K. Proposed photoionization mechanisms appear to be excluded. Rapid ionization of the ions requires that the heating occur sufficiently low in the corona that the electron density exceed about (1-5) x 10 to the 8th/cu cm. Heavy-element enhancements might be a signature of material processed in the flash phase of events in contrast to unheated ambient material accelerated by a coronal shock.

Reames, D. V.↗
NASA NTRS1988

An unusual charging event on ISEE 1

Electrostatic cleanliness requirements on ISEE 1 were expected to prevent negative charging in sunlight. This has largely been true, but on three occasions, ISEE 1 has been observed to charge to significant negative potentials in sunlight. Data from the two electric field experiments and from the plasma composition experiment on ISEE 1 show that the spacecraft charged to close to -70 V in sunlight at about 0700 UT on March 17, 1978. Data from the electron spectrometer experiment show that there was a potential barrier of some -10 to -20 V about the spacecraft during this event. The potential barrier was effective in turning back emitted photoelectrons to the spacecraft. Potential barriers can be formed by differential charging on the spacecraft or by the presence of excess space charge in the plasma. The shape of the barrier suggests that it is due to the former, even though electrostatic cleanliness specifications imposed on ISEE were intended to eliminate differential charging. Modeling of this event showed that the barrier could not be produced by the presence of space charge but that it was most likely produced by differential charging of the solar arrays.

Olsen, R. C.↗
NASA NTRS1987

Simultaneous radio and white light observations of the 1984 June 27 coronal mass ejection event

Two-dimensional images of radio bursts in the 25-50-MHz frequency range obtained with the SMM Coronagraph/Polarimeter and Mauna Loa K-coronameter during a coronal mass ejection event on June 27, 1984 are discussed. The present event is shown to be spatially and temporally associated with precursors in the form of meter-decameter type III bursts, soft X-ray emission, and a H-alpha flare spray. The results suggest gyrosychrotron emission from a plasmoid containing a magnetic field of about 2.5 G and nonthermal electrons with a number density of about 100,000/cu cm and energy of greater than about 350 keV.

Gopalswamy, N.↗
NASA NTRS1988

Downstream energetic proton and alpha particles during quasi-parallel interplanetary shock events

This paper considers the energetic particle populations in the downstream region of three quasi-parallel interplanetary shock events, which was explored using the ISEE 3 Ultra Low Energy Charge Analyzer sensor, which unambiguously identifies protons and alpha particles using the electrostatic deflection versus residual energy technique. The downstream particles were found to exhibit anisotropies due largely to convection in the solar wind. The spectral indices of the proton and the alpha-particle distribution functions were found to be remarkably constant during the downstream period, being generally insensitive to changes in particle flux levels, magnetic field direction, and solar wind densities. In two of the three events, the proton and the alpha spectra were the same throughout the entire downstream period, supporting the prediction of diffusive shock acceleration theory.

Tan, L. C.↗
NASA NTRS1988

High-ozone events in Atlanta, Georgia, in 1983 and 1984

Measurements of ozone levels and meterological parameters were analyzed to determine the relative importance of transport-related processes and photochemical production in causing high-ozone events in and around the Atlanta metropolitan area. Back-trajectories calculated by the Branching Air Trajectory Model indicate that the air associated with high-ozone events had often traveled a significant distance within the previous 3 days: for days with ozone levels above 100 ppbv, half of the calculated trajectories showed that the air had traveled over 600 km, with half of those coming from the northwest quadrant. Six-hour vector-averaged winds were used to find that the concentrations of ozone in the air leaving the metropolitan area averaged 20-40 ppbv more than that entering the area.

Lindsay, Ronald W.↗
NASA NTRS1988

Photometry of Pluto-Charon mutual events and Hirayama family asteroids

Once every 124 years, nature provides earth-bound astronomers with the opportunity to observe occultation and transit phenomena between Pluto and its satellite, Charon. Ground-based observations of these events will allow precise physical parameters for the Pluto-Charon system to be derived which are unlikely to be improved upon until in situ spacecraft observations are obtained. The proposed program will continue to support photometry observations from McDonald Observatory, a critical location in an international Pluto Campaign network. Knowledge of the diameters, masses, densities, and compositions derived from these observations will augment our understanding of Pluto's origin and its context within the problem of solar system formation. A second task will continue to research the evolutionary processes which have occurred in the asteroid belt by measuring the physical properties of specific Hirayama family members. Photoelectric lightcurve observations of Koronis and Themis family members will be used to investigate the individual catastrophic collision events which formed each family. By comparing these properties with results of laboratory and numerical experiments, the outcomes of catastrophic disruptions and collisional evolution may be more precisely determined.

Binzel, Richard P.↗
NASA NTRS1988

Heavy ion induced Single Event Phenomena (SEP) data for semiconductor devices from engineering testing

The accumulation of JPL data on Single Event Phenomena (SEP), from 1979 to August 1986, is presented in full report format. It is expected that every two years a supplement report will be issued for the follow-on period. This data for 135 devices expands on the abbreviated test data presented as part of Refs. (1) and (3) by including figures of Single Event Upset (SEU) cross sections as a function of beam Linear Energy Transfer (LET) when available. It also includes some of the data complied in the JPL computer in RADATA and the SPACERAD data bank. This volume encompasses bipolar and MOS (CMOS and MHNOS) device data as two broad categories for both upsets (bit-flips) and latchup. It also includes comments on less well known phenomena, such as transient upsets and permanent damage modes.

Nichols, Donald K.↗
NASA NTRS1988

Magnetic microspherules associated with the K/T and upper Eocene extinction events

Magnetic microspherules were identified in over 20 K/T boundary sites, and in numerous Deep Sea Drilling Project (DSDP) cores from the Caribbean and Pacific, synchronous with the extinction of several radiolarian species near the end of the Eocene. The K/T magnetic spherules are of particular interest as carriers of Ir and other siderophiles generally found in abundance in K/T boundary clay. Furthermore the textures and unusual chemistry of their component magnetic phases indicate an origin at high temperature, possibly related to (an) unusual event(s) marking the end of the Cretaceous and Eocene periods. Their origin, along with the non-magnetic (sanidine) spheules, is generally ascribed directly to megaimpact events hypothesized to have periodically disrupted life on Earth. A survey of microspherical forms associated with known meteorite and impact derived materials reveals fundamental differences from the extinction related spherules. Low temperature magnetic experiments on the K/T and Upper Eocene spheroids indicate that, unlike tektites, extremely small superparamagnetic carriers are not present in abundance. The extensive subaerial exposure of Cretaceous combustible black shale during sea level regression in the latest Cretaceous represents a potential source for the magnetic spheroids found in certain K/T boundary clays. The recent discovery of high Ir abundances distributed above and below the K/T boundary within shallow water sediments in Israel, which also contain the most extensive known zones of combustion metamorphism, the so called Mottled Zone, adds a further dramatic footnote to the proposed association between the magnetic spheroids and combustion of organic shales. Interestingly, the Mottled Zone also contains the rare mineral magnesioferrite, which was identified both within the K/T magnetic spheroids and as discrete crystals in boundary clay from marine and continental sites.

Cisowski, Stanley M.↗
NASA NTRS1988

Iridium abundance measurements across bio-event horizons in the geological record

Geochemical studies have been performed on thousands of rock samples collected across bio-event horizons in the fossil record using INAA for about 40 common and trace elements and radiochemical isolation procedures for Os, Ir, Pt, and Au on selected samples. These studies were begun soon after the Alvarez team announced their discovery of the Cretaceous-Tertiary (K-T) Ir anomaly in marine rock sequences in Europe. With their encouragement the Authors searched for the anomaly in nearby continental (freshwater coal swamp) deposits. In collaboration with scientists from the U.S.G.S. in Denver, the anomaly was located and it was observed that a floral crisis occurred at the same stratigraphic position as the Ir spike. Further work in the Raton Basin has turned up numerous well-preserved K-T boundary sections. Although the Authors have continued to study the K-T boundary and provide geochemical measurements for other groups trying to precisely locate it, the primary effort was turned to examining the other bio-events in the Phanerozoic, especially to those that are older than the terminal Cretaceous. A list of horizons that were examined in collaboration with paleontologists and geologists is given. Results are also given and discussed.

Orth, C. J.↗
NASA NTRS1988

Pressure-strain-rate events in homogeneous turbulent shear flow

A detailed study of the intercomponent energy transfer processes by the pressure-strain-rate in homogeneous turbulent shear flow is presented. Probability density functions (pdf's) and contour plots of the rapid and slow pressure-strain-rate show that the energy transfer processes are extremely peaky, with high-magnitude events dominating low-magnitude fluctuations, as reflected by very high flatness factors of the pressure-strain-rate. A concept of the energy transfer class was applied to investigate details of the direction as well as magnitude of the energy transfer processes. In incompressible flow, six disjoint energy transfer classes exist. Examination of contours in instantaneous fields, pdf's and weighted pdf's of the pressure-strain-rate indicates that in the low magnitude regions all six classes play an important role, but in the high magnitude regions four classes of transfer processes, dominate. The contribution to the average slow pressure-strain-rate from the high magnitude fluctuations is only 50 percent or less. The relative significance of high and low magnitude transfer events is discussed.

Brasseur, James G.↗
NASA NTRS1988

No effect of diffraction on Pluto-Charon mutual events

Mulholland and Gustafson (1987) made the interesting suggestion that observations of Pluto-Charon mutual events might show significant dependence on both wavelength and telescope aperture because of diffraction effects. In this letter, observations are presented that show the predicted effects to be absent and demonstrate that the parameters of the system are such that the events can be accurately analyzed with geometrical optics.

Tholen, D. J.↗
NASA NTRS1989

Solar sources of interplanetary southward Bz events responsible for major magnetic storms (1978-1979)

The solar sources of interplanetary southward Bz events responsible for major magnetic storms observed in the August 1978-December 1979 period were studied using a full complement of solar wind plasma and field data from ISEE 3. It was found that, of the ten major storms observed, seven were initiated by active region flares, and three were associated with prominence eruptions in solar quiet regions. Nine of the storms were associated with interplanetary shocks. However, a comparison of the solar events' characteristics and those of the resulting interplanetary shocks indicated that standard solar parameters did not correlate with the strengths of the resulting shocks at 1 AU.

Tang, Frances↗
NASA NTRS1989

Discrete events and solar wind energization

Based on a multiple-magnetic-reconnection picture, an estimation of the energy flux suggests that small-scale EUV exploding events may contribute a significant amount of energy (of order of 100,000 erg/sq cm sec) to solar atmospheric heating and solar-wind acceleration. Most of the dissipated magnetic energy is converted into thermal energy and plasma turbulence. On a related aspect, a numerical study based on the nonlinear one-fluid hydrodynamic equations shows a self-smoothing effect, whereby a multistream structure of the solar wind formed near the sun can be gradually smoothed during its propagation through interplanetary space. This calculation gives support for the possible contribution of discrete energetic events to high-speed solar wind streams.

Yang, W.-H.↗
NASA NTRS1989

Interplanetary energetic particle observations of the March 1989 events

The IMP-8 spacecraft placed in an elongated orbit of approximately R(sub E) x R(sub E) orbit around the Earth was the only monitor of the energetic particle environment of the near interplanetary space during the period of the solar particle events associated with the Active Region 5395 in March 1989. Measurements of energetic ion and electron intensities were obtained in a series of channels within the energy range: 0.3 to 440 MeV for photons, 0.6 to 52 MeV/nuc for alpha particles, 0.7 to 3.3 MeV/nuc for nuclei with Z greater than or equal to 3, 3 to 9 MeV/nuc with Z greater than or equal to 20, and 0.2 to 2.5 MeV for electrons. The responses of selected energy channels during the period 5 to 23 March 1989 are displayed. It is clearly noted that the most prominent energetic ion intensity enhancements in that time interval were associated with the interplanetary shock wave of March 13 (07:42 UT) as well as that of March 8 (17:56 UT), which have distinct particle acceleration signatures. These shock waves play a major role in determining the near Earth energetic ion intensities during the above period by accelerating and modulating the ambient solar energetic particle population, which was already present in high intensities in the interplanetary medium due to the superposition of a series of solar flare particle events originating in AR 5395. The differential ion intensities at the lowest energy channel of the CPME experiment, which were associated with the March 13 shock wave, reached the highest level in the life of the IMP-8 spacecraft at this energy. At high energies, the shock associated intensity peak was smaller by less than a factor of 3 than the maxima of solar flare particle intensities from some other major flares, in particular from those with sites well connected to the Earth's magnetic flux tubes.

Sarris, E. T.↗