Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “wave data”

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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Atmospheric effects on RF propagation due to turbulence in the Venus atmosphere

Although there have been several theoretical studies and predictions of the Venus atmospheric effects on the radio-frequency wave propagation, the limited experimental data of Venera 4, 5, 6 and 7 do not provide a consistent answer on how severe the turbulence effects could be especially near the Venus surface. In this paper the status of this problem is examined. Important theoretical results are presented. Some meaningful conclusions are drawn from the available experimental data as well as the theoretical analysis.

Chen, C. H.↗
NASA NTRS1974

High energy galactic gamma radiation from cosmic rays concentrated in spiral arms

A model for the emission of high energy ( 100 MeV) gamma rays from the galactic disk was developed and compared to recent SAS-2 observations. In the calculation, it is assumed that (1) the high energy galactic gamma rays result primarily from the interaction of cosmic rays with galactic matter; (2) on the basis of theoretical and experimental arguments the cosmic ray density is proportional to the matter density on the scale of galactic arms; and (3) the matter in the galaxy, atomic and molecular, is distributed in a spiral pattern consistent with density wave theory and the experimental data on the matter distribution.

Bignami, G. F.↗
NASA NTRS1974

A multi-satellite study of the nature of wavelike structures in the magnetospheric plasma

An intercomparison is made of the wavelike structures in the data from the light ion mass spectrometer and the fluxgate magnetometer on OGO 5. The wavelike structures appear simultaneously in the data from both experiments. The waves contain both transverse and compressional modes and exhibit periods of 100 to 200 seconds. The waves are usually observed outside the plasmapause and are located primarily on the dayside of the magnetosphere. One possible cause of the apparent density fluctuation is a velocity modulation of the thermal plasma which causes the particles to drift into and out of the ion spectrometer.

Shelley, E. G.↗
NASA NTRS1975

OGO-V radio burst analysis

An analysis is presented of data on the km-wave type-3 bursts associated with H alpha flares. A list of published papers based on previous analysis is also presented.

Haddock, F. T.↗
NASA NTRS1977

Theory of ultrasonic diffraction by damage developed in thin laminated composites

The apparent attenuation which would result if certain damage states (transverse cracks and delaminations) are introduced into a graphite/epoxy laminate through which an ultrasonic wave passes is investigated. Experimental data for two different laminates are presented which shows changes in the apparent attenuation of about one db. These changes generally occur at loads which correspond to the range predicted for the formation of the damage. The predicted changes in the attenuation for several simple and common damage states are well within the range of experimental values.

Hayford, D. T.↗
NASA NTRS1980

On the polarization state of hydromagnetic fluctuations in the solar wind

From presently available observations it can be inferred that the Alfvenic turbulence measured in the solar wind, predominantly on trailing edges of high speed streams, is a mixture of modes with two different polarizations, namely, Alfvenic modes and modes which are the incompressible limit of slow magnetosonic waves. Using Helios 2 magnetic data and a variance analysis, parallel (to the mean field) and perpendicular components of the fluctuations are separated and the possible correlation between such components is studied. Correlations between eigenvalues of the variance matrix are also investigated and discussed.

Bavassano, B.↗
NASA NTRS1981

On the polarization state of hydromagnetic fluctuations in the solar wind

From presently available observations one can infer that the Alfvenic turbulence measured in the solar wind, predominantly on trailing edges of high-speed streams, is a mixture of modes with two different polarizations, namely, Alfvenic modes and modes which are the incompressible limit of slow magnetosonic waves. Using Helios 2 magnetic data and a variance analysis, parallel (to the mean field) and perpendicular components of the fluctuations are separated, and the possible correlation between such components which would be predicted as a consequence of the incompressible character of the turbulence is studied. Correlations between eigenvalues of the variance matrix are also investigated and discussed.

Bavassano, B.↗
NASA NTRS1983

Uppermantle anisotropy and the oceanic lithosphere

Published Rayleigh and Love wave phase and group velocity data have been inverted taking into account sphericity, anelastic dispersion, and transverse isotropy. For a PREM-type modular parameterization, the thickness of the high velocity mantle seismic lithosphere (LID) varies in thickness from about 30 km for young ocean to about 50 km for old ocean, much less than previous estimates based on isotropic inversion of similar data. This LID thickness is comparable to the elastic or flexural thickness found from studies of seamount loading and flexure at trenches, suggesting that the thickness of the lithosphere may be controlled by mineralogy, composition, or crystal orientation rather than by temperature alone.

Anderson, D. L.↗
NASA NTRS1984

Teleseismic array analysis of upper mantle compressional velocity structure

Relative array analysis of upper mantle lateral velocity variations in southern California, analysis techniques for dense data profiles, the P-wave upper mantle structure beneath an active spreading center: the Gulf of California, and the upper mantle under the Cascade ranges: a comparison with the Gulf of California are presented.

Walck, M. C.↗
NASA NTRS1983

Determination of vertical and horizontal wavelengths of gravity waves

The determination of horizontal and vertical wavelengths of gravity waves obviously relies on measurement of wave parameters in horizontal and vertical directions. A very suitable parameter, measured fairly easily with MST radars, is the fluid velocity. Average velocities and superimposed turbulent fluctuations are much larger in the horizontal than in the vertical direction. Vertical and horizontal fluid velocities due to wave-like events are mostly about equal in magnitude. Vertical fluid velocities due to waves therefore can be more reliably detected than horizontal velocities. Estimates of gravity wave events using MST radar data are calculated and results are indicated.

Rottger, J.↗
NASA NTRS1983

Remote sensing of oceanographic parameters pertinent to hydrocarbon resource development

Information obtained from remotely sensed imagery which is potentially useful to hydrocarbon resource development is discussed in this paper. Oceanic phenomena presented include surface gravity waves, detection of bathymetric features, and deep ocean internal waves. Techniques used to extract data are presented along with pertinent examples.

Kasischke, E. S.↗
NASA NTRS1984

Suprathermal ions upstream from interplanetary shocks

Low energy (10 eV-30 keV) observations of suprathermal ions ahead of outward propagating interplanetary shock waves (ISQ) are reported. The data were taken with the fast plasma experiment on ISEE 1 and 2 during 17 events. Structure was more evident in the suprathermal ion distribution in the earth bow shock region than in the upstream region. Isotropic distributions were only observed ahead of ISW, although field alignment, kidney-bean distributions, ion shells in velocity space and bunches of gyrating ions were not. The data suggest that the solar wind ions are accelerated to suprathermal energies in the vicinity of the shocks, which feature low and subcritical Mach numbers at 1 AU.

Gosling, J. T.↗
NASA NTRS1984

Changes in the Ozone Content over Central Europe During Reversals of Stratospheric Circulation in Late Winter

A superposed epoch analysis during late winter zonal wind reversals was carried out from 18 year observation series (1963 to 1980) of the meridional geopotential height gradient in the 30 mb level (latitude mean) and of the ozone content over central Europe. Experimental data suggest that if planetary waves are responsible for the additional meridional ozone transport during stratospheric warmings, this transport has to take place at heights other than those up to the ozone maximum in the middle latitudes.

Entzian, G.↗
NASA NTRS1985

The influence of tropical wind data on the analysis and forecasts of the GLAS GCM for the Global Weather Experiment

Several densities of tropical divergent wind data were included in a fourth-order GCM to examine the effects on the accuracy of the model predictions. The experiments covered assimilation of all available tropical wind data, no tropical wind data between 20 deg N and 20 deg S, only westerly tropical wind data and only easterly tropical wind data. The predictions were all made for the 200 mb upper troposphere. Elimination of tropical data produced excessively strong upper tropospheric westerlies which in turn amplified the globally integrated rotational flow kinetic energy by around 10 percent and doubled the global divergent flow kinetic energy. Retaining only easterly wind data, ameliorated most of the error. Inclusion of all the tropical wind data however, did not lead to overall positive effects, as the data were linked to tropical wave energetics and ageostrophic winds which were already assimilated in the model.

Paegle, J.↗
NASA NTRS1987

Steady bimodal convection in a cylinder at large Prandtl numbers

Steady bimodal convection of an infinite Prandtl-number Boussinesq fluid in a cylinder is considered. An asymptotic analysis similar to the one used by Buell and Catton (1986) for axisymmetric convection yields a solvability condition that determines the radial wavenumber. The analysis is valid for convection far away from the origin, the lateral boundary, and any pattern dislocations. The azimuthal wave number is treated as a parameter, although in real systems it is dependent on the initial and boundary conditions. Results are presented for Rayleigh numbers between 14,000 and 60,000, and for azimuthal wave numbers between 5 and 7. It is shown that for increasing Rayleigh numbers, the selected radial wave number and the heat transfer tend to become independent of the azimuthal wave number. No quantitative experimental data are available, but one qualitative comparison is good.

Buell, Jeffrey C.↗
NASA NTRS1989

Observations of low-frequency radio emissions in the earth's magnetosphere

Electromagnetic radiation in the earth's magnetosphere was investigated for the frequency range between 10 kHz and 80 kHz, using data from the Minnesota Plasma Wave Experiment aboard the IMP 6 spacecraft. Two types of radio emissions were examined, the first being the nonthermal continuum radiation, and the second, much more impulsive, is the radiation which lies between 10 and 60 kHz. The first type of radiation was found to correlate with the enhancements of the magnetic substorm index AE and to follow the onset of the negative bay feature of the AU index by about 20 min. The second radiation was found to correlate with auroral kilometric radiation (AKR) on a time scale of about 1 min; this radiation was found to have a source direction very near that of the coincident AKR.

Filbert, Paul C.↗
NASA NTRS1990

Particle simulation of ion heating in the ring current

Heating of heavy ions has been observed in the equatorial magnetosphere in GEOS 1 and 2 and ATS 6 data due to ion cyclotron waves generated by anisotropic hot ring current ions. A one-dimensional hybrid-Darwin code has been developed to study ion heating in the ring current. Here, a strong instability and heating of thermal ions is investigated in a plasma with a los cone distribution of hot ions. The linear growth rate calculation and particle simulations are conducted for cases with different loss cones and relative ion densities. The linear instability of the waves, the quasi-linear heating of cold ions and dependence on the thermal H(+)/He(+) density ratio are analyzed, as well as nonlinear parallel heating of thermal ions. Effects of thermal oxygen and hot oxygen are also studied.

Qian, S.↗
NASA NTRS1989

High-speed digital fiber optic links for satellite traffic

Large aperture phased array antennas operating at millimeter wave frequencies are designed for space-based communications and imaging platforms. Array elements are comprised of active T/R modules which are linked to the central processing unit through high-speed fiber-optic networks. The system architecture satisfying system requirements at millimeter wave frequency is T/R level data mixing where data and frequency reference signals are distributed independently before mixing at the T/R modules. This paper demonstrates design procedures of a low loss high-speed fiber-optic link used for transmission of data signals over 600-900 MHz bandwidth inside satellite. The fiber-optic link is characterized for transmission of analog and digital data. A dynamic range of 79 dB/MHz was measured for analog data over the bandwidth. On the other hand, for bursted SMSK satellite traffic at 220 Mbps rates, BER of 2 x 10 to the -7th was measured for E(b)/N(o) of 14.3 dB.

Daryoush, A. S.↗