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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 325 records · Page 18
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NASA NTRS1975

Apparent relationship between solar sector boundaries and 300-millibar vorticity: Possible explanation in terms of upward propagation of planetary-scale waves

The correlations between the solar sectors and large-scale atmospheric vorticity in the lower atmosphere reported earlier are of interest since the solar-sector data appear to be independent of any terrestrial influences. It is shown that even these solar data may be affected by geomagnetic properties; a method for removing such influences is suggested.

Deland, R. J.↗
NASA NTRS1976

Electron precipitation in the postmidnight sector of the auroral zones

Measurements of the angular distributions and energy spectra of electron intensities within the energy range 50 eV to 15 keV with electrostatic analyzer arrays on board the low-altitude satellite Injun 5 are reported for the postmidnight sector of the auroral zones during the high-intensity events accompanying magnetic substorms. Precipitation features on closed terrestrial field lines well equatorward of the trapping boundary for electrons with energies greater than 45 keV are examined. Precipitation of low-energy electron intensities was characterized by isotropy for all pitch angles outside the atmospheric backscatter cone. The region of electron precipitation observed is associated with the diffuse aurora and with pulsating aurora in the postmidnight sector. Similar variations of the energetic electron intensities with energies above 45 keV were observed in the regions of fluctuating energy fluxes of low-energy electrons associated with auroral luminosity. The increases of energetic electron intensities were not coincident with those of the principal energy fluxes into the atmosphere, except when the average electron energy for the energy fluxes was unusually high, i.e., in the 10-keV range. Precipitation of electron intensities within these energy ranges is consistent with strong pitch angle diffusion of electron intensities near or at the magnetic equator by high-frequency wave turbulence, the effectiveness of which is modulated by perturbations attributable to micropulsations.

Frank, L. A.↗
NASA NTRS1976

Simultaneous observations of field-aligned currents and particle fluxes in the post-midnight sector

The paper presents several examples of simultaneous measurements of electrons and positive ions (5 eV to 15 eV) and of magnetic field perturbations due to field-aligned currents made on the polar-orbiting ISIS-2 satellite at 1400 km altitude in the early morning local time (MLT) sector. There is a good general correspondence between changes in the gradient of the E-W component of the magnetic field along the spacecraft orbit and changes in the character of the low-energy electron fluxes. The equatorward region of outward current flow in this post-midnight sector is spatially coincident with the isotropic precipitation associated with the low-altitude plasma sheet. In cases examined, electron current density always exceeds positive ion current density by a factor of 10 and usually by a factor of over 100.

Klumpar, D. M.↗
NASA NTRS1975

Sector-scanning echocardiography

The mechanical sector scanner is described in detail, and its clinical application is discussed. Cross sectional images of the heart are obtained in real time using this system. The sector scanner has three major components: (a) hand held scanner, (b) video display, and (c) video recorder. The system provides diagnostic information in a wide spectrum of cardiac diseases, and it quantitates the severity of mitral stenosis by measurement of the mitral valve orifice area in diagnosing infants, children and adults with cyanotic congenital heart disease.

Henry, W. L.↗
NASA NTRS1977

Computer program for flat sector thrust bearing performance

A versatile computer program is presented which achieves a rapid, numerical solution of the Reynolds equation for a flat sector thrust pad bearing with either compressible or liquid lubricants. Program input includes a range in values of the geometric and operating parameters of the sector bearing. Performance characteristics are obtained from the calculated bearing pressure distribution. These are the load capacity, center of pressure coordinates, frictional energy dissipation, and flow rates of liquid lubricant across the bearing edges. Two sample problems are described.

Presler, A. F.↗
NASA NTRS1978

Process heat in California: Applications and potential for solar energy in the industrial, agricultural and commercial sectors

A summary of the results of a survey of potential applications of solar energy for supplying process heat requirements in the industrial, agricultural, and commercial sectors of California is presented. Technical, economic, and institutional characteristics of the three sectors are examined. Specific applications for solar energy are then discussed. Finally, implications for California energy policy are discussed along with recommendations for possible actions by the State of California.

Barbieri, R. H.↗
NASA NTRS1978

Interplanetary gas. XXII - Plasma tail disconnection events in comets - Evidence for magnetic field line reconnection at interplanetary sector boundaries

Attention is focused on a form of cometary activity which has been known for some time but is poorly understood: the discarding of a plasma tail by a comet. A link is found between plasma-tail rejections and conditions in the solar wind. A model is presented in which a disconnected tail is the end result of magnetic-field-line reconnection in the cometary ionosphere caused by the traversal of a magnetic sector boundary. Observations of plasma tails appear to be the best and only method at present of mapping the interplanetary sector structure out of the ecliptic plane.

Niedner, M. B., Jr.↗
NASA NTRS1979

Tropospheric circulation and interplanetary magnetic sector boundaries followed by MeV proton streams

The MeV proton streams which Svestka et al. (1976) connected with certain sector boundary transits appear to select boundary transits associated with unusually active solar wind conditions. Changes in tropospheric circulation linked to the proton boundary transits were larger than those linked to other boundary transits observed during the same interval. This investigation of sector boundary transits also sheds light on the relationship between changes in solar wind velocity, density and magnetic field and terrestrial changes in the vorticity area index, geomagnetic activity, and cosmic ray flux at earth.

Wilcox, J. M.↗
NASA NTRS1980

Fine-scale characteristics of interplanetary sector

The structure of the interplanetary sector boundaries observed by Helios 1 within sector transition regions was studied. Such regions consist of intermediate (nonspiral) average field orientations in some cases, as well as a number of large angle directional discontinuities (DD's) on the fine scale (time scales 1 hour). Such DD's are found to be more similar to tangential than rotational discontinuities, to be oriented on average more nearly perpendicular than parallel to the ecliptic plane to be accompanied usually by a large dip ( 80%) in B and, with a most probable thickness of 3 x 10 to the 4th power km, significantly thicker previously studied. It is hypothesized that the observed structures represent multiple traversals of the global heliospheric current sheet due to local fluctuations in the position of the sheet. There is evidence that such fluctuations are sometimes produced by wavelike motions or surface corrugations of scale length 0.05 - 0.1 AU superimposed on the large scale structure.

Behannon, K. W.↗
NASA NTRS1981

Interplanetary gas. XXVI - On the reconnection of magnetic fields in cometary ionospheres at interplanetary sector boundary crossings

The reconnection process in the cometary ionosphere believed responsible for the disconnecting plasma tails phenomenon is studied through the basic equations of reconnection theory and current sheet instability criteria. It is proposed that reconnection occurs when the interplanetary magnetic fields incident on a comet that has gone just past a sector boundary are pressed into the fields captured from the previous sector. The fields are of opposite polarity, and the previously captured fields constitute the 'roots' of the plasma tail. An estimated duration of reconnection during a disconnection event (DE) of 0.75 days is used along with estimates of other cometary parameters to construct fusion region dimensions and resistivity with the adopted time scale.

Niedner, M. B., Jr.↗
NASA NTRS1981

Fine-scale characteristics of interplanetary sector boundaries

The study examines the structure of the interplanetary sector boundaries observed by Helios 1 within sector transition regions during the time interval from December 1974 to April 1975. The transition regions are found to be complex in character, consisting of intermediate average field orientations in some cases as well as a number of large-angle directional discontinuities (DDs). It is suggested that the observed DDs represent multiple traversals of the global heliospheric current sheet caused by local fluctuations in the position of the sheet. There is evidence that such fluctuations are sometimes produced by wavelike motions or surface corrugations of scale length 0.05-0.1 AU, superimposed on the large-scale structure.

Behannon, K. W.↗
NASA NTRS1982

Structure of current sheets in the sector boundaries - Helios 2 observations during early 1976

The orientation and structure of 14 current sheets are examined. Most of the observed sheets can be interpreted as tangential discontinuities that are, on the average, inclined at large angles with respect to the ecliptic plane, and have a typical thickness ranging from 1000 to 6000 km. Results do not show any evidence for a variation of the physical characteristics of the boundaries with time or heliocentric distances. The implications of a comparison between present results and the global configuration of the sector boundary surface are discussed, and it is concluded that the multiplicity of events within individual transition regions may suggest fluctuations of the sector boundary surface on the fine scale.

Villante, U.↗
NASA NTRS1984

Observations of interplanetary energetic ion enhancements near magnetic sector boundaries

All the energetic medium-nuclei (carbon, nitrogen, and oxygen) flux increases observed by the satellites IMP 7 and IMP 8 at 1 AU during Bartels rotations 1906-1974 are examined. After removing flare-related increases, the remaining 145 events were compared to interplanetary-maganetic-field and solar-wind parameters. A class of flux enhancements is discovered in which the ion increases occur close to the onset of magnetic-sector boundary crossings. This observation is interpreted as a facilitated access to 1 AU of energetic ions from the corona or chromosphere via the magnetic-sector structure. It appears that this access is more significant for medium than for lighter nuclei, suggesting a possible charge or rigidity-dependent transport mechanism.

Briggs, P. R.↗
NASA NTRS1984

Relationship of dusk sector radial electric field to energy dispersion at the inner edge of the electron plasma sheet

It is shown that, by assuming that the magnetospheric particle boundaries are the result of steady state convection, the electron boundaries in the dusk sector are essentially sensitive to the local, not the global, electric field configuration. A simple, direct relationship is obtained between the dusk sector radial electric field and the inner edge of electron boundaries at various energies.

Horwitz, J. L.↗
NASA NTRS1984

Solar Flare and IMF Sector Structure Effects in the Lower Ionosphere

About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L = 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (= magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

Lastovicka, J.↗
NASA NTRS1986

Relations between morning sector Pi 1 pulsation activity and particle and field characteristics observed by the DE 2 satellite

Ground-based magnetometer, photometer, and riometer data are combined with low-altitude particle and electric and magnetic field data from the DE-2 spacecraft to provide a more complete characterization of the magnetospheric and tropospheric environment in which morning sector asymmetric Pi 1 pulsations are observed. The results of the study are in agreement with recent conclusions that morning sector asymmetric Pi 1 pulsations are physically related to pulsating aurorae. Precipitation of energetic electrons (E greater than 35 keV) coincides in every instance with the occurrence of these pulsations.

Engebretson, M. J.↗
NASA NTRS1987

An eastward propagating compressional Pc 5 wave observed by AMPTE/CCE in the postmidnight sector

This paper presents a detailed analysis of a compressional Pc 5 wave observed in the postmidnight sector on July 21, 1986, using data from the magnetometer, the charge-energy-mass spectrometer, and the medium-energy particle analyzer aboard the AMPTE/Charge Composition Explorer (CCE) spacecraft. The Pc 5 wave exhibited harmonically related transverse and compressional magnetic oscillations, modulation of the flux of medium energy protons, and a large azimuthal wave number, i.e., properties that are similar to those of compressional Pc5 waves observed previously at geostationary orbit. The unique observations recorded by the AMPTE/CCE included the occurrence of the wave in the postmidnight sector, its sunward propagation with respect to the spacecraft, and the left-handed polarization of the perturbed magnetic field. In spite of the morphological uniqueness observed, the excitation of the July 21 event is considered to be due to the same type of instability as operates at geostationary orbit.

Takahashi, K.↗
NASA NTRS1989

Spatial variation and evolution of heliospheric sector structure

The magnetic sector polarity at the sun and in the IMF was surveyed during about three quarters of sunspot cycle 21 using ground-based photospheric magnetic field observations and spacecraft observations, including Voyagers 1 and 2 and Pioneer Venus Orbiter data. The location of the heliospheric current sheet near the sun throughout the period 1977-1985 is calculated. The large-scale magnetic polarity structure was in almost continuous evolution throught this period. IMF polarity patterns derived from spacecraft data are compared with the pattern observed at the sun, showing that sector pattern stability decreases with increasing heliocentric distance.

Behannon, K. W.↗