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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

DE 2 observations of disturbances in the upper atmosphere during a geomagnetic storm

Results are presented of physical interpretations of a sequence of in situ measurements taken in the midlatitude dusk sector during the geomagnetic storm of November 24, 1982 by instruments on board the DE-2 spacecraft in polar orbit. The results represent the first comparison of nearly simultaneous measurements, obtained at different seasons in a common local time sector, of storm disturbances in dc electric fields, zonal ion convection, zonal winds, gas composition and temperature, and electron density and temperature.

Miller, N. J.↗
NASA NTRS1991

Solar cycle variation in the subauroral electron temperature enhancement - Comparison of AE-C and DE 2 satellite observations

The elevation of the subauroral electron temperature is one of the phenomena showing the energy transfer from the magnetosphere and the response of the ionosphere. This study addresses solar cycle variations in the subauroral Te peak by comparing observations of the subauroral peak by the Atmosphere Explorer C (AE-C) satellite near solar minimum (1974 and 1977) with similar observations by the Dynamics Explorer 2 (DE 2) satellite near solar maximum (1981-1982). Te peaks with magnitudes sufficient to produce observable stable auroral red arc emissions occurred more frequently during solar maximum than in solar minimum, but the variation in the magnitudes and positions of these peaks with magnetic activity did not change significantly with solar cycle. These results are discussed in terms of the solar cycle changes in the ionosphere and the magnetospheric energy source.

Fok, M.-C.↗
NASA NTRS1990

DE-2 observations of filamentary currents at ionospheric altitudes

Conjunctive measurements made by the Dynamics Explorer 1 and 2 spacecraft on October 22, 1981, under conditions of southward IMF, suggest the existence of a cusp ion injection from a region at the magnetopause with a scale size of about 1/2 to 1 earth radii. Current signatures observed by the LAPI and MAGB instruments on board DE-2 indicate the existence of a rotation in the magnetic field that is consistent with a filamentary current system. The observed current structure can be interpreted as the ionospheric signature of a flux transfer event (FTE). In addition to this large-scale current structure there exist three small-scale filamentary current pairs. These current pairs close locally and thus, if the present interpretation of this event as an FTE is correct, represent the first reported observations of FTE interior structure at low-altitudes.

Smith, M. F.↗
NASA NTRS1992

Enhancement of Shubnikov-de Haas Oscillations by Carrier Modulation

A novel technique for drastically enhancing the Shubnikov-de Haas (SdH) pattern of oscillatory magnetoresistance is presented. The technique is based on measuring the change in the magnetoresistance due to a carrier generated by a modulated light source. The technique also has the important property of selectively increasing the amplitude of the slower oscillations due to carriers in the second subband much more than oscillations generated by the ground subband electrons. Very clear oscillations generated by a carrier concentration well below 5 x 10 exp 10/sq cm were recorded using the technique.

Schacham, S. E.↗
NASA NTRS1992

Correlation between magnetic and electric field perturbations in the field-aligned current regions deduced from DE 2 observations

The satellite-observed high correlations between magnetic and electric field perturbations in the high-latitude field-aligned current regions are investigated by examining the dependence of the relationship between Delta-B and E on spatial scale, using the electric and magnetic field data obtained by DE 2 in the polar regions. The results are compared with the Pedersen conductivity inferred from the international reference ionosphere model and the Alfven wave velocity calculated from the in situ ion density and magnetic field measurements.

Ishii, M.↗
NASA NTRS1992

A DE-1/whistler study of the thermal plasma structure and dynamics in the dusk bulge sector of the magnetosphere

The objective of this research was to obtain new understanding of the thermal plasma structure and dynamics of the plasmasphere bulge region of the magnetosphere, with special emphasis on the erosion process that results in a reduction in plasmasphere size and on the manner in which erosion leads to the presence of patches of dense plasma in the middle and outer afternoon-dusk magnetosphere. Case studies involving data from the DE 1, GEOS 2, and ISEE 1 satellites and from ground whistler stations Siple, Halley, and Kerguelen were used. A copy of the published paper entitled 'A case study of plasma structure in the dusk sector associated with enhanced magnetospheric convection,' is included.

Carpenter, D. L.↗
NASA NTRS1993

The algebra of supertraces for 2+1 super de Sitter gravity

The algebra of the observables for 2+1 super de Sitter gravity, for one genus of the spatial surface is calculated. The algebra turns out to be an infinite Lie algebra subject to non-linear constraints. The constraints are solved explicitly in terms of five independent complex supertraces. These variables are the true degrees of freedom of the system and their quantized algebra generates a new structure which is referred to as a 'central extension' of the quantum algebra SU(2)q.

Urrutia, L. F.↗
NASA NTRS1992

The quiet time polar cap - DE 1 observations and conceptual model

A conceptual merging model of the magnetosphere is developed which explains DE-1 observations on polar cap plasmas and waves made during a quiet period with a northward IMF when multiple adjacent regions of sunward and antisunward convection were observed. The model involves dayside merging both at high latitudes on open field lines (the usual northward IMF merging) and at lower latitudes on closed field lines. The ratio between the merged flux produced by the high-latitude merging to that produced by the lower-latitude merging increases as the IMF becomes more northward.

Burch, J. L.↗
NASA NTRS1993

Characterization of the IMF By-dependent field-aligned currents in the cleft region based on DE 2 observations

The magnetic field and plasma data from 47 passes of DE-2 are used to study the IMF By-dependent distribution of field-aligned currents in the cleft region. It is proposed that the low-latitude cleft current (LCC) region is not an extension of the region 1 or region 2 current system and that a pair of LCCs and high-latitude cleft currents (HCCs) constitutes the cleft field-aligned current regime. The proposed pair of cleft field-aligned currents is explained with a qualitative model in which this pair of currents is generated on open field lines that have just been reconnected on the dayside magnetopause. The electric fields are transmitted along the field lines to the ionosphere, creating a poleward electric field and a pair of field-aligned currents when By is positive; the pair of field-aligned currents consists of a downward current at lower latitudes and an upward current at higher latitudes. In the By negative case, the model explains the reversal of the field-aligned current direction in the LCC and HCC regions.

Taguchi, S.↗
NASA NTRS1993

High-latitude distributions of plasma waves and spatial irregularities from DE 2 alternating current electric field observations

The high-latitude spatial distributions of average signal intensities in 12 frequency channels between 4 Hz and 512 kHz as measured by the ac electric field spectrometers on the DE-2 spacecraft are analyzed for 18 mo of measurements. In MLT-INL (magnetic local time-invariant latitude) there are three distinct distributions that can be identified with 4-512 Hz signals from spatial irregularities and Alfven waves, 256-Hz to 4.1-kHz signals from ELF hiss, and 4.1-64 kHz signals from VLF auroral hiss, respectively. Overlap between ELF hiss and spatial irregularity signals occurs in the 256-512 Hz band. VLF hiss signals extend downward in frequency into the 1.0-4.1 kHz band and upward into the frequency range 128-512 kHz. The distinctly different spatial distribution patterns for the three bands, 4-256 Hz, 512-1204 Hz, and 4.1-64 kHz, indicate a lack of any causal relationships between VLF hiss, ELF hiss, and lower-frequency signals from spatial irregularities and Alfven waves.

Heppner, J. P.↗
NASA NTRS1993

De-Dopplerization of aircraft acoustic signals

A de-Dopplerization scheme is devised and applied to both a tonal noise source, a XV-15 aircraft, and a broadband noise source, a F-18 aircraft. The procedure is developed from the conservation equations of fluid mechanics and is described in the paper. The corrected time history is constructed by using linear interpolation in the measured time history. This was made possible by knowing the position history of the aircraft provided by radar and/or laser tracking. The XV-15 data established that the scheme can accurately account for Doppler frequency shifts. The F-18 data confirms what has been noted in prediction models and static tests pertaining to broadband shock associated noise. That is, the peak frequency increases and the peaks broaden toward the jet axis. Another issue addressed in the study is the influence of correcting for spherical spreading and Doppler amplitude on the spectral shape and overall sound pressure levels of the source. Results from this investigation confirm that the dominant noise source in high-speed jets is due to turbulent mixing.

Kelly, Jeffrey J.↗
NASA NTRS1993

DE 1 particle and wave observations in Auroral Kilometric Radiation (AKR) source regions

The high-altitude plasma instrument on board the DE 1 satellite was operating during several near crossings of the AKR source in the nightside auroral region. Observations of electron distributions indicate a region of perpendicular heating adjacent to, and within, the source region. Loss cones, trapped particles, beams, and electron conical distributions are also observed near and within the source region, which extends perpendicular to the magnetic field line for at least 20 km. Near the AKR source region wave-particle interactions appear to have modified the observed electron distributions. We compare the observations to those predicted by recently published numerical simulations.

Menietti, J. D.↗
NASA NTRS1993

Warm O(+) polar wind and the DE-1 polar cap electron density profile

Theoretical steady state semikinetic polar wind density profiles, based on DE1/RIMS polar wind data (up to 3700 km), were obtained which agree very well with the power law electron density profile measured by the DE1/PWI for high altitudes. The polar wind is found to be O(+) dominated for the full altitude range considered (up to 8 R(E)). Multiple solutions are obtained for various combinations of base altitude ion temperatures and electron temperatures, such that the densities fit the Persoon et al. (1983) profile. For example, good fits to measured density profile are found for low base ion temperatures (5000 K) and high electron temperatures (9000 K), and also for unheated H(+) and O(+)(3000 K) with electron temperatures of 11,000 K. Below 2.8 R(E) the theoretical polar wind density deviates somewhat from the r exp -3.85 power law. It is concluded that this theoretical polar wind density profile, with a sum of base electron and ion temperatures of 14,000 K, yields a close match with the measured DE-1 electron density profile.

Ho, C. W.↗
NASA NTRS1926

A New De Havilland Commercial Airplane : the D.H. 66 with Three Bristol "jupiter" Engines

The D.H. 66, constructed at Stag Lane Works of the De Haviland Aircraft Company built for Imperial Airways, Ltd. The fuselage has an all steel construction while the wings are made with box spars of wood and spruce ribs. It has a biplane tail and encloses the stabilizer trimming gear in a casing which serves to streamline the rear portion of the fuselage, but which is not part of the main structure. It weighs 9060 lbs. empty and 2500 lbs. after fueling with a total loaded weight of 14,700 lbs.

AIRPLANES - DES↗
NASA NTRS1926

The De Havilland "Moth"

Officially designated D.H. 60, De Havilland's Moth is a small, simply made, 770 lb. aircraft. It has had it's fittings reduced in number to assist in this, seats 2 (including pilot) and uses a Cirrus 60 HP. engine.

AIRPLANES - DEHAVILLAND 60 MOTH (BRIT )↗
NASA NTRS1927

The De Havilland "Tiger Moth"a low wing monoplane

With a speed of 186.5 M.P.H. and an operational altitude of 20,000 feet the De Havilland Tiger Moth has caused comment as it was introduced just before the King's Cup race of 1927. It is a single seater with unusual control configuration due to the cramped cockpit area.

AIRPLANES - DEHAVILLAND TIGER MOTH (BRIT )↗