Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “E”

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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Ionospheric D and E regions

Some areas of D and E region research are examined, with particular reference to the photochemistry and transport of minor neutral constitutents in the mesosphere and lower thermosphere. The review shows that the D and E regions become more complex physical and chemical systems as research progresses, so that some previous views on these regions have to be revised. In particular, the lower ionosphere appears to be hydrodynamically coupled to the lower atmosphere and electrodynamically coupled to the magnetosphere.

Sechrist, C. F., Jr.↗
NASA NTRS1975

Effect of electric fields on the daytime high-latitude E and F regions

We have obtained solutions of the coupled continuity, momentum, and energy equations for NO(+), O(+), and O2(+) ions for conditions appropriate to the daytime high-latitude E and F regions. Owing to the rapid increase of the reaction O(+) + N2 yielding NO(+) + N with ion energy, high-latitude electric fields and consequent perpendicular-E x B drifts deplete O(+) in favor of NO(+). For electric field strengths less than about 10 mV/m the depletion of O(+) is small, and the altitude profiles of ion density are similar to those found at mid-latitudes. However, for moderate electric field strengths (50 mV/m), NO(+) is substantially increased in relation to O(+) and becomes an important ion throughout the F region. For large electric fields (200 mV/m), NO(+) completely dominates the ion composition to at least 600 km, decreasing at high altitudes with a diffusive equilibrium scale height. Since the overall F region electron density decreases markedly with increasing electric field strength, it appears that high-latitude, daytime electron density troughs are directly related to the presence of ionospheric electric fields.

Schunk, R. W.↗
NASA NTRS1976

An analysis of auroral E region neutral winds based on incoherent scatter radar observations at Chatanika

The physical origin of auroral E-region neutral winds during geomagnetic disturbances is investigated by comparing incoherent-backscatter radar observations made at Chatanika, Alaska, during such disturbances with detailed theoretical calculations of neutral velocities for these conditions. In the analysis, an ion-drag collisional-coupling model is adopted as the primary driving force for the neutral winds. Electric fields and electron number densities observed by the radar facility are used in the calculations, and the coupled ion and neutral momentum equations are solved numerically as functions of altitude and time in the ion-drag approximation. The altitude structure of the velocity field is examined, and the detailed response of the neutral gas to the ion-drag mechanism is delineated. Weighted altitude averages of the calculated velocities are obtained, the accuracy of the procedure for deriving neutral winds from incoherent-scatter radar observations is evaluated, and the comparison is carried out. It is concluded that both ion drag and pressure gradients appear to be required to explain the neutral winds observed in the auroral E-region during geomagnetic disturbances.

Comfort, R. H.↗
NASA NTRS1977

An experiment to measure variations in nighttime E-region neutral concentration

An experimental procedure is demonstrated which holds promise for the nighttime measurement of ion-neutral collision frequencies or net neutral concentration in the E-region by combining incoherent scatter data with appropriate photometric measurements. Data illustrating the technique are applied to comparing relative variations in atomic oxygen concentrations (from the E-region component of the O I 5577 A emission) near 100 km to those in the net neutral concentration obtained from combined incoherent scatter data and neutral temperature data extracted from Fabry-Perot measurement of the O I 5577 A line profile.

Cogger, L. L.↗
NASA NTRS1977

Reflection of radio waves by sporadic-E layers

A full-wave analysis of the reflection coefficient is developed and applied to electron-density profiles of midlatitude sporadic-E layers observed by rocket-borne probes. It is shown that partial reflection from the large electron-density gradients at the upper and lower boundaries of sporadic-E layers does not account for the partial transparency observed by ionosondes.

Miller, K. L.↗
NASA NTRS1977

The magnetic attitude control of the Atmosphere Explorer-E spacecraft

The Atmosphere Explorer-E spacecraft was launched in November 1975, as the last of the Atmosphere Explorer series. It is a dual spin satellite and has on-board magnetic coils to maintain the spin axis of the spacecraft within 2 degrees of orbit normal. There is a constraint on the total angular momentum to keep it at a constant level, at around 1200 in-lb-sec +/-10 percent. On the previous AE satellites, the attitude and momentum were controlled separately, with dipoles mounted parallel to the spin axis for pure attitude control, and with coils in the spin plane to desaturate the momentum wheel. Due to the near-equatorial orbit of the AE-E spacecraft, spin axis coils would be inefficient, because the dipoles would have been closely aligned with the geomagnetic field vector. For this reason it was decided to control both attitude and momentum magnitude with dipoles in the spin plane. However, for spin plane coils the attitude and momentum control are strongly coupled, which required a special control theory to be worked out.

Grell, M. G.↗
NASA NTRS1980

Status of linear boundary-layer stability and the e to the nth method, with emphasis on swept-wing applications

The-state-of-the-art for the application of linear stability theory and the e to the nth power method for transition prediction and laminar flow control design are summarized, with analyses of previously published low disturbance, swept wing data presented. For any set of transition data with similar stream distrubance levels and spectra, the e to the nth power method for estimating the beginning of transition works reasonably well; however, the value of n can vary significantly, depending upon variations in disturbance field or receptivity. Where disturbance levels are high, the values of n are appreciably below the usual average value of 9 to 10 obtained for relatively low disturbance levels. It is recommended that the design of laminar flow control systems be based on conservative estimates of n and that, in considering the values of n obtained from different analytical approaches or investigations, the designer explore the various assumptions which entered into the analyses.

Hefner, J. N.↗
NASA NTRS1979

Morphology and phenomenology of the high-latitude E and F regions

Results obtained at high latitude observatories on the behavior of E and F region ionization are presented including a bibliography. Behavior of E and F region ionization during day and night for quiet and disturbed conditions in the auroral and polar regions is described. Daily, seasonal and sunspot variations are also outlined.

Hunsucker, R. D.↗
NASA NTRS1980

Rocket measurements of electron temperature in the E region

The rocket borne equipment, experimental method, and data reduction techniques used in the measurement of electron temperature in the E region are fully described. Electron temperature profiles from one daytime equatorial flight and two nighttime midlatitude flights are discussed. The last of these three flights, Nike Apache 14.533, showed elevated E region temperatures which are interpreted as the heating effect of a stable auroral red arc.

Zimmerman, R. K., Jr.↗
NASA NTRS1979

On the inference of properties of Saturn's Ring E from energetic charged particle observations

The paper demonstrates that information about Saturn's Ring E particle size is potentially obtainable from observations of Saturnian trapped radiation. It is shown that observations of the radial dependence of the intensities, energy spectra, electron-to-proton intensity ratio, and pitch angle distributions of energetic charged particles trapped outside of Ring A can potentially provide information (1) on the existence of Ring E, (2) on the effective size of the particulate matter therein, and (3) on the magnitude of the radial diffusion coefficient for energetic particles. A parametric study of these possibilities is specialized to the characteristics of the University of Iowa detectors on Pioneer 11 which was scheduled to make a close encounter with Saturn in 1979.

Thomsen, M. F.↗
NASA NTRS1978

Ionospheric scintillations associated with equatorial E-region

Amplitude scintillations at 40, 140, and 360 MHz recorded at an equatorial station Ootacamund (dip 4 deg N) during the ATS-6 phase II and the ionograms at a nearby station Kodaikanal (dip 3.5 deg N) are examined for the scintillation activity. Various sporadic E events, but not the Es-q, are associated with intense daytime scintillations. There are no scintillations at times of normal E-layer or cusp type of Es. Scintillations are also present at times of night Es.

Chandra, H.↗
NASA NTRS1980

Cosmic noise 'absorption' by E region plasma waves

Riometer records and the electric field records obtained during the same period at two different locations are compared in order to investigate the effect of cosmic radio wave backscatter by E region plasma waves on the cosmic radio wave power reaching riometers. The data on the relation between absorption events of small magnitude (a few tenths of a decibel to about 1 dB) and intense ionospheric electric fields are in agreement with the idea that a number of absorption events measured by riometers result from radiation backscatter into space by E region plasma waves of the Farley-Buneman type.

Mehta, N. C.↗
NASA NTRS1981

Midlatitude sporadic-E layers

Rocket borne probes and incoherent scatter radar were demonstrated to be effective methods of studying the structure of midlatitude sporadic E layers. Layers are formed when metal ions are converged vertically in a wind shear to produce a local enhancement of electron density. Rocket and radar observations show that the layers may occassionally have complex structure produced by an unstable wind shear. The partial transparency to radio waves of sporadic E layers is shown to be due to localized regions of high electron density.

Smith, L. G.↗
NASA NTRS1980

Sporadic-E layers and unstable wind shears

Electron density profiles of sporadic-E layers have been observed with good height resolution using rocket-borne probes. These generally show a simple shape consistent with the effect of a linear wind shear acting on metallic ions. Occasionally more complex shapes have been recorded, including double peaks and, on one occasion, a nearly rectangular profile. A direct method of obtaining the wind profile from the concentration profile of metallic ions has been developed. The metallic ion concentration profile itself is obtained from the electron density profile. Both procedures derive from the steady-state continuity equation. For linear wind shears it is found that the maximum value of the shear is about 50 m/s/km which corresponds to a Richardson number of 1/4. Layers of complex shape are associated with non-linear wind shears in which the maximum shear considerably exceeds this value. It is concluded that the complex profiles of sporadic-E layers can be interpreted as an effect of unstable wind shears.

Smith, L. G.↗
NASA NTRS1981

EUV flux variations during solar cycle 21 from AE-E He/+/ abundances

The ionization rate of helium in the thermosphere is inferred from AE-E ion and neutral particle composition measurements, made on several days during solar cycle 21, in the context of a steady state photochemical model for helium ions. The inferred ionization rate varies by a factor of 4 between July 1976 and January 1979, a value consistent with the variation in the flux measured during the same period by the EUV spectrometer on board the AE-E satellite.

Oppenheimer, M.↗
NASA NTRS1981

Infrared reflection nebulae in S 106 and NGC 7538 E

Two micron linear polarimetry of the S 106 and NGC 7538 E regions reveal the presence of infrared reflection nebulae, which may confuse the count of luminosity sources in a region of star formation. S 106 and NGC 7538/IRS 9 are considered the only luminosity sources in their respective regions, and the polarization of S 106/Source 3 is probably due to absorption by aligned grains. Moreover, the reflection nebula model for NGC 7538 E is best supported if the polarization of NGC 7538/IRS 9 itself is due to the absorption by aligned grains.

Tokunaga, A. T.↗
NASA NTRS1982

Short-term EUV flux variations from AE-E He/+/ abundances

The ionization rate of helium in the thermosphere is inferred from AE-E ion and neutral particle composition measurements made on 20 days from January 1979 to June 1980. The variations in the inferred rate are consistent with variations in the UV flux measured during the same period by the AE-E UV spectrometer. The approximately 27-day modulation of the calculated ionization rate is the result of cyclical variations in the UV flux, which are in turn coupled to the rotation period of the sun. Results indicate that the ionization structure of helium in the thermosphere is closely coupled to both the long and short term EUV flux variations.

Sternberg, A.↗
NASA NTRS1982

Nucleosynthesis in novae - A source of Ne-E and Al-26

It is shown upon computation of the nucleosynthesis products of explosive hydrogen burning, in the framework of recent nova models, that nova condensates will probably contain isotopic anomalies in Ne-22, from Na-22 decay, and Mg-26, from Al-26 decay. It is found, for all the models considered, that while too much Ne-20 and -21 is produced relative to Ne-22 to explain the presumably almost pure Ne-22 meteoritic Ne-E component, the Na-22 abundance is high enough to explain Ne-E as its decay product if nova condensates are preserved in Ne samples. It is also determined that while Al-26 is coproduced with Na-22, its total amount strongly depends on the uncertain, Si-27(p, gamma)P-28 reaction rate. The abundances of all nuclides, up to Ar, are computed and found to be clearly nonsolar in many cases.

Hillebrandt, W.↗