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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

IMF orientation, solar wind velocity, and Pc 3-4 signals - A joint distribution

Separate studies using the same micropulsation data base in the period range 10-150 s have shown earlier that signal levels recorded during September, October, and November 1969 at Calgary correlated positively with both solar-wind alignment of the IMF and solar-wind speed, but each correlation contained enough scatter to allow for the influence of the other factor. In this report, joint correlations of velocity and field direction with parameters representing hourly distributions rather than minima of IMF orientation angle display the relative effect of the two agents on magnetic pulsation signal levels. The joint correlations reduce the overall scatter and show that solar-wind speeds above 200-300 km/s and angles between the IMF and the sun-earth line of less than 50-60 deg are associated with enlarged magnetic pulsation amplitudes. These threshold effects tend to support both the bow-shock origin and the Kelvin-Helmholtz amplification of daytime signal transients in the Pc 3, 4 period ranges.

Greenstadt, E. W.↗
NASA NTRS1979

Satellite observations of the spatial extent and structure of Pc 3, 4, 5 pulsations near the magnetospheric equator

Simultaneous observations of Pc 3, 4, 5 pulsations by five satellites in the pre-noon local time sector at and near synchronous orbit are examined. The periods of these simultaneous pulsations are not the same at the different observation points. This difference is attributed to site dependent resonant conditions. The spatial properties of the temporal phenomenon are demonstrated with observations by ISEE-1 and -2 as they pass through oscillations in a spatially limited region. Fundamental and second harmonic standing Alfven waves are observed simultaneously on the same field line. The periods are consistent with model predictions when the measured plasma composition, which by mass consists mainly of singly ionized oxygen, is taken into account.

Singer, H. J.↗
NASA NTRS1982

Pc 1-2 magnetic pulsation spectra and heavy ion effects at synchronous orbit - ATS 6 results

Two types of Pc 1-2 wave events have been identified in ATS 6 flux gate magnetometer data recorded approximately 12 deg off the geomagnetic equator. Left-hand polarized waves observed in the afternoon are typical of IPDP ground events. Highly elliptical and linearly polarized waves occur around local noon. Spectra often show slots near the equatorial helium and oxygen cyclotron frequencies. The linear polarization may be interpreted in terms of propagation at a large wave normal angle or a crossover frequency that is a consequence of propagation in a multicomponent plasma. The spectral slots may be associated with either heavy ion cyclotron resonanace or propagation effects.

Fraser, B. J.↗
NASA NTRS1982

A cross spectral analysis of high-latitude Pc 5 pulsations in the morning sector

An analysis of the spatial phase and amplitude structures of the ground Pc 5 pulsations in the morning sector was carried out using data from the North American IMS magnetometer network. Signals in the X, Y, and Z components were found to propagate from noon to the nightside with an apparent phase velocity of 13 km/sec. The phase was determined to vary with latitude, with total latitudinal phase differences of 200 and 90 deg, respectively, for the X and Y components. Corresponding latitudinal phase differences in the vertical components were 550 deg for the Alaska chain, and 360 deg for the Fort Churchill chain. Phase variation in the Fort Churchill chain was attributed to the ionospheric Hall current related to the field line resonance and the earth induction current. The earth induction current in the shallower regions near Fort Yukon is a necessary factor to explain the large variation in the Alaska chain.

Saka, O.↗
NASA NTRS1982

Pc 1-2 observations of heavy ion effects by synchronous satellite ATS-6

Ion cyclotron waves generated in the magnetosphere by the ion cyclotron instability of protons are thought to be the origin of Pc 1-2 geomagnetic pulsations. Propagation characteristics of these waves have been measured using ATS-6 synchronous satellite magnetometer wave data. Of particular interest are the wave spectra, polarization properties, and wave diagnostics; all are characteristic of propagation in a cool ambient magnetospheric plasma containing He(+) and O(+) heavy ions.

Fraser, B. J.↗
NASA NTRS1983

Comparison of phase and amplitude structures of Pc 5 pulsations in the morning and afternoon sectors

North American IMS magnetometer network data are used in comparisons of the spatial phase and amplitude structures of the morning and afternoon Pc 5 pulsations, using cross spectral analysis of phase and amplitude readings between different stations. The spatial phase structures are found to be very similar in the morning and afternoon sectors for each of the three components. Amplitudes are larger in the magnetic north than in the magnetic east components for both sectors. Latitudinal amplitude and phase difference variations between the magnetic north and east components exhibit dissimilarities in the morning and afternoon sectors. These results suggest that compressional mode magnetic field oscillations are not observable on the ground in this time sector. The pulsations in both time sectors are instead seen as caused by transverse mode magnetospheric field oscillations.

Saka, O.↗
NASA NTRS1983

The rate of occurrence of dayside Pc 3,4 pulsations - The L-value dependence of the IMF cone angle effect

When the angle of the IMF to the earth sun line is 15 deg or less, the occurrence rate of dayside Pc 3,4 pulsations in 7-8 times the average at L values of 2.4-2.8, and 2.2-3.5 times the average at L of 4-4.3. These waves disappear when the IMF is nearly at right angles to the sun-earth line. Such observations are consistent with a source originating in the waves upstream of the subsolar bow shock, which are transported by convection to the magnetopause. There, they couple to oscillations of magnetospheric field lines. Because the magnetospheric plasma's index of refraction decreases with radial distance except at the plasmapause, inwardly propagating waves should be refracted away from the radial direction. To reach low L values, the waves should therefore couple near the stagnation point and propagate nearly radially inwards. The streamline geometry and its connection to the foreshock region is illustrated for various IMF orientations, using a simple approximation to the magnetosheath flow field.

Russell, C. T.↗
NASA NTRS1984

Dependence of the spectrum of Pc 3-4 pulsations on the interplanetary magnetic field

Dependence of the power spectrum of Pc 3-4 magnetic pulsations observed at the ATS 6 geosynchronous satellite on the interplanetary magnetic field (IMF) has been studied. Pulsation events that were observed near noon and exhibited harmonic structure are chosen for analysis. Further selected are pulsation events with identical fundamental frequency to study dependence of the power of pulsations at different harmonic bands on the IMF. A weak negative correlation is observed between the IMF cone angle theta-XB and the power of pulsations in the frequency range 20-70 mHz. Also, a positive correlation between the intensity of the IMF B(IMF) and the power of pulsations at 50-70 mHz is found. This B(IMF) control is present at all ranges of the cone angle. A comparison is conducted of this observation with the frequency of bow shock associated upstream waves predicted from a model of wave generation by a cyclotron resonance of ions reflected at the bow shock. The predicted frequency depends on the IMF as B(IMF) (cos theta-XB)-squared. Although this relation gives a proportionality between the frequency and B(IMF) qualitatively consistent with the observation, it does not explain the most obvious IMF control of the spectrum of the pulsations.

Takahashi, K.↗
NASA NTRS1984

Detection of narrow C 4 and Si 4 absorption features in spectra of stars within 200 pc f the Sun

Detection of narrow (Beta lambda 0.5 A) absorption features in C 4 at lambda lambda 1548 and 1550 have been made in the spectra of 4 late B dwarfs within 200 pc of the Sun; the Si4 doublet at lambda lambda 1393 and 1403 shows up in two of them. It is argued that it is difficult to account for the strengths, widths, shapes, and C IV/Si IV ratios in terms consistent with a circumstellar origin except possibly for an asymmetric C IV component in one star (HD 185037). The most probable source is semi-torrid gas in the 50,000 K range forming the interfaces between cooler H 1 clouds and the ambient medium at coronal temperatures. Late B rapid rotators are used for local interstellar medium probing of this kind.

Molaro, P.↗
NASA NTRS1984

Molecular Clouds Within 100 Pc

Observations at the 2.6 mm line of CO reveal the presence of a large number of molecular clouds at high galactic latitude. If the velocity dispersion of the clouds is a measure of their scale height, the mean distance of the ensemble detected is 100 pc. The clouds are unusual in that either they are not gravitationally bound or they are very deficient in CO relative to molecular hydrogen. These clouds represent a heretofore unrecognized component of the local interstellar medium. If they are pervasive in the Milky Way, they probably represent the small molecular cloud component of the interstellar medium.

Blitz, L.↗
NASA NTRS1986

NASTRAN data deck generation on the PC

Using two commercial programs an application was developed to aid in generating a run-ready NASTRAN data deck on the PC. Macros are used to access relevant reference material and card files while editing the deck. The application can be easily customized to suit individual or group needs.

Guyan, R. J.↗
NASA NTRS1986

Wave and plasma observations during a compressional Pc 5 wave event August 10, 1982

Magnetometer and thermal plasma instruments on the polar-orbiting Dynamics Explorer 1 satellite observed a small-amplitude ultralow frequency pulsation event at the outer edge of the plasmapause near the geomagnetic equator in the midafternoon sector on August 10, 1982, during the recovery phase of a magnetic storm. Transverse pulsations of 30-50 s period were observed throughout the event, and a 270-s period, purely compressional Pc 5 pulsation with several shifts in phase occurred within + or - 5 deg of the geomagnetic equator. Electric fields and the motion of thermal ions appeared to be in quadrature with pulsations in magnetic field magnitude throughout the event. This suggests that the net Poynting flux for the compressional waves was zero, consistent with their being standing waves. Large fluxes of trapped 90 deg pitch angle 10-eV protons, also symmetric about the geomagnetic equator, were observed in conjunction with the waves. These may serve as a source of free energy for the pulsations. These observations lend support to recent studies suggesting that many dayside compressional wave events are related to localized field line resonance near plasmapauselike boundaries, but also include features that cannot be explained by existing theories.

Engebretson, M. J.↗
NASA NTRS1987

AKPLOT: A plotter routine for IBM PC, XT and AT

The AKPLOT software for the IBM PC, XT, and AT is an efficient and versatile tool that allows X-Y plotting of quantitative information. Features include IBM four-color graphics, which combined with 10 different symbols allows 40 different curves on the same grid, shrink or expansion of the graph size, any combination of log and linear X and Y axes, selective plotting from multiple curves of a previous run, interpolation and polynomial least-squares fit with any degree polynomial, and a 90-degree tilt of the entire graph. These options are independent, and can be invoked individually.

Kantak, Anil↗
NASA NTRS1986

A storm time, Pc 5 event observed in the outer magnetosphere by ISEE 1 and 2 - Wave properties

The properties of the waves composing a classical storm time Pc 5 event, recorded by the satellite pair ISEE 1,2 during an inbound nearly equatorial pass in the dusk sector on August 21-22, 1978, are described. On the basis of these observations it is concluded that the events of the August 21-22 pass resulted from a combination of sources, namely, distant wideband excitation and ion drift instability, plus a coupling of wave modes. It is suggested that the observed phenomenon was a radial cross section of the type of event reported by Barfield et al. (1972).

Greenstadt, E. W.↗
NASA NTRS1987

A model for the harmonic of compressional Pc 5 waves

Compressional Pc 5 magnetic waves in the magnetosphere are a unique phenomenon showing a nonsinusoidal waveform in spite of a well-defined period. Although the waveform can be Fourier-decomposed into the fundamental and the second harmonics, the phase between the two is kept constant from event to event, implying that the waveform is not the result of a chance superposition of two magnetospheric eigenmodes. A phenomenological explanation to this waveform is offered using a field-line configuration model that is a modified version of a previously proposed antisymmetric standing wave. In this model, the location of the equatorial node of field-line displacement is assumed to oscillate with the wave, with a peak-to-peak amplitude greater than 10 percent of the wavelength of the standing wave. The predicted waveform at various magnetic latitudes is found to be in excellent agreement with an observation taken near the magnetic equator by the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer spacecraft.

Takahashi, K.↗
NASA NTRS1987

Simultaneous observation of Pc 3-4 pulsations in the solar wind and in the earth's magnetosphere

The equatorially orbiting Active Magnetospheric Particle Tracer Explorers CCE and IRM satellites have made numerous observations of Pc 3-4 magnetic field pulsations (10-s to 100-s period) simultaneously at locations upstream of the earth's bow shock and inside the magnetosphere. These observations show solar wind/IMF control of two categories of dayside magnetospheric pulsations. Harmonically structured, azimuthally polarized pulsations are commonly observed from L = 4 to 9 in association with upstream waves. More monochromatic compressional pulsations are clearly evident on occasion, with periods identical to those observed simultaneously in the solar wind. The observations reported here are consistent with a high-latitude (cusp) entry mechanism for wave energy related to harmonically structured pulsations.

Engebretson, M. J.↗
NASA NTRS1987

Personal Computer (PC) based image processing applied to fluid mechanics

A PC based image processing system was employed to determine the instantaneous velocity field of a two-dimensional unsteady flow. The flow was visualized using a suspension of seeding particles in water, and a laser sheet for illumination. With a finite time exposure, the particle motion was captured on a photograph as a pattern of streaks. The streak pattern was digitized and processed using various imaging operations, including contrast manipulation, noise cleaning, filtering, statistical differencing, and thresholding. Information concerning the velocity was extracted from the enhanced image by measuring the length and orientation of the individual streaks. The fluid velocities deduced from the randomly distributed particle streaks were interpolated to obtain velocities at uniform grid points. For the interpolation a simple convolution technique with an adaptive Gaussian window was used. The results are compared with a numerical prediction by a Navier-Stokes computation.

Cho, Y.-C.↗
NASA NTRS1987

AUTOPLAN - A PC-based automated mission planning tool

A PC-based automated mission and resource planning tool, AUTOPLAN, is described, with application to small-scale planning and scheduling systems in the Space Station program. The input is a proposed mission profile, including mission duration, number of allowable slip periods, and requirement profiles for one or more resources as a function of time. A corresponding availability profile is also entered for each resource over the whole time interval under study. AUTOPLAN determines all integrated schedules which do not require more than the available resources.

Paterra, Frank C.↗