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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Predictability of upper-atmospheric density and composition

Empirical models of upper-atmospheric density and composition are employed in a number of areas, ranging from basic research in atmospheric and ionospheric physics to practical applications in satellite ephemeris prediction. Such models are based on various kinds of data sets and have varying levels of complexity, strengths, and weaknesses. The characteristics of several of the widely used models are described and studies in which the predictions of these models were compared with observational data are reviewed. The relative advantages and limitations of the models in current use are discussed as well as ways in which the models might be improved.

Straus, J. M.↗
NASA NTRS1987

Theoretical study of the effect of ionospheric return currents on the electron temperature

A time-dependent, three-dimensional model of the high-altitude ionosphere is presently used to study the effects of field-aligned ionospheric return currents on auroral electron temperatures for different seasonal and solar cycle conditions, as well as for different upper boundary heat fluxes. The average, large scale, return current densities, which are a few microamps/sq m, are too small to affect auroral electron temperatures. The thermoelectric effect exhibits a pronounced solar cycle and seasonal dependence, and its heat transport corresponds to an upward flow of electron energy which can be either a source or sink of electron energy depending on altitude and geophysical conditions.

Schunk, R. W.↗
NASA NTRS1984

Thermal fluctuations from an artificial ion beam injection into the ionosphere

Simulations of argon beam experiments flown on two sounding rocket flights (ARCS 1, 2) reveal two bands of electrostatic wave emissions, one at high frequencies around the upper hybrid mode, the other at low frequencies around the lower hybrid mode. The latter is significantly enhanced by the argon beam in the simulations, and the enhancement was clearly observed on ARCS 2. This enhancement at phase velocities greater than the beam velocity is suggested to be due to an increase in the thermal fluctuation level of the plasma when the argon beam is present. Inclusion of electron dynamics and oblique angles of wave propagation with respect to B allows investigation of electron heating. Electron tail heating is observed parallel to B for k-parallel/k-perpendicular proportional to the square root of m(e)/m(0), while background ions are heated perpendicular to B.

Hudson, M. K.↗
NASA NTRS1963

An Analysis of the Second Project High Water Data

Early in 1962 NASA established "Project High Water" to investigate the sudden release of large quantities of water into the upper atmosphere. The primary objectives of these experiments were to obtain information on the behavior of liquids released in the ionosphere and the localized effects on the ionosphere produced by the injection of large quantities of water. The data obtained in the two (2) Project High Water experiments have yielded an extensive amount of information concerning the complex phenomena associated with the sudden release of liquids in the Ionosphere. The detailed analysis of data obtained during the second Project High Water experiment (i.e., the third Saturn I vehicle test or SA-3) presented in this report demonstrates that the objectives of the Project High Water were achieved. In addition, the Project High Water has provided essential information relevant to a number of problems vital to manned explorations of space.

Woodbridge, David D.↗
NASA NTRS1993

F region plasma drifts over Arecibo - Solar cycle, seasonal, and magnetic activity effects

Characteristics of low-latitude F region plasma drifts are determined on the basis of Arecibo incoherent scatter measurements from 1981 to 1990. The measurements show large day-to-day variability even during magnetically quiet periods. The average poleward/perpendicular plasma drifts do not change significantly with season and solar cycle except in the midnight-morning sector. The zonal drifts show clear solar cycle and seasonal effects. The plasma drifts along the magnetic field lines exhibit large altitudinal and seasonal variations, particularly near solar minimum, and are generally anticorrelated with the perpendicular/north drifts. The drift patterns observed by the Arecibo and the middle and upper atmosphere radars have significantly different seasonal dependences. This is explained by electrodynamic effects in the corresponding local and conjugate ionospheres.

Fejer, B. G.↗
NASA NTRS1991

Interpretation of Voyager UVS observations of occultations by the atmosphere of Neptune

We propose to continue our investigation of the upper atmosphere of Neptune based primarily on the solar occultation measurements made by the Voyager Ultraviolet Spectrometer (UVS). The ultimate goal of this research is to understand the structure and composition of Neptune's upper atmosphere as encoded in the data base obtained by the UVS during the Voyager 2 encounter with Neptune. The UVS occultations provide information essential to studies of atmospheric composition and structure, energy balance, photochemistry, global transport, ionospheric structure, and airglow production mechanisms. In conjunction with other research in progress at the University of Arizona and by our colleagues at other institutions, we not only analyze and interpret individual measurements or observations by the UVS, but also construct models of the upper atmosphere which are consistent with all available data obtained by the UVS. We derive constraints from measurements of the atmospheric emissions and we combine these with constraints derived from the occultation measurements. Principal sources for the atmospheric emissions include dayglow, resonance scattering and, at long wavelengths, the reflected solar spectrum. On the dark side of the planet, a weak H Ly alpha emission is due to resonance scattering of the sky background and perhaps another source. Thus a wide range of physical processes are at work, and each provides its own constraints on the atmosphere.

Sandel, Bill R.↗
NASA NTRS2013

Superthermal Electron Energy Interchange in the Ionosphere-Plasmasphere System

A self-consistent approach to superthermal electron (SE) transport along closed field lines in the inner magnetosphere is used to examine the concept of plasmaspheric transparency, magnetospheric trapping, and SE energy deposition to the thermal electrons. The dayside SE population is generated both by photoionization of the thermosphere and by secondary electron production from impact ionization when the photoelectrons collide with upper atmospheric neutral particles. It is shown that a self-consistent approach to this problem produces significant changes, in comparison with other approaches, in the SE energy exchange between the plasmasphere and the two magnetically conjugate ionospheres. In particular, plasmaspheric transparency can vary by a factor of two depending on the thermal plasma content along the field line and the illumination conditions of the two conjugate ionospheres. This variation in plasmaspheric transparency as a function of thermal plasma and ionospheric conditions increases with L-shell, as the field line gets longer and the equatorial pitch angle extent of the fly-through zone gets smaller. The inference drawn from these results is that such a self-consistent approach to SE transport and energy deposition should be included to ensure robustness in ionosphere-magnetosphere modeling networks.

Heliophysics↗
NASA NTRS1981

H2 abundance in the atmosphere of Venus

The in situ measurements from the Pioneer Venus Orbiter (PVO) Ion Mass Spectrometer have led to the detection of H2(+) ions in the Venus ionosphere. Although H2(+) is a minor ion, its measurement provides the first direct clue for determining the H2 abundance in the upper atmosphere of Venus. A photochemical model using PVO measurements is used to derive an H2 mixing ratio of 10 ppm below 140 km altitude. The presence of this much H2 confirms a previous prediction that the reactions of O(+) with H2 and subsequent recombination of OH(+) provide an important source of nonthermal H observed in the Venus atmosphere. The estimated escape flux for H is 10 to the 8th per sq cm/s.

Kumar, S.↗
NASA NTRS1983

A thermal oscillating two-stream instability

A theory for the oscillating two-stream instability, in which the Ohmic heating of the electrons constitutes the nonlinearity, is developed for an inhomogeneous and magnetized plasma. Its possible role in explaining short-scale, field-aligned irregularities observed in ionospheric heating experiments is emphasized. The theory predicts that the initial growth of such irregularities is centered around the level of upper hybrid resonance. Furthermore, plane disturbances nearly parallel to the magnetic meridian plane have the largest growth rates. Expressions for threshold, growth rate, and transverse scale of maximum growth are obtained. Special attention is paid to the transport theory, since the physical picture depends heavily on the kind of electron collisions which dominate. This is due to the velocity dependence of collision frequencies, which gives rise to the thermal forces

Dysthe, K. B.↗
NASA NTRS1986

Microwave emission and scattering from Earth surface and atmosphere

Nonlinear Electromagnetic (EM) wave interactions with the upper atmosphere were investigated during the period 15 December 1985 to 15 June 1986. Topics discussed include: the simultaneous excitation of ionospheric density irregularities and Earth's magnetic field fluctuations; the electron acceleration by Langmuir wave turbulence; and the occurrence of artificial spread F. The role of thermal effects in generating ionospheric irregularities by Whistler waves, intense Quasi-DC electric fields, atmospheric gravity waves, and electrojets was investigated. A model was developed to explain the discrete spectrum of the resonant ultralow frequency (ULF) waves that are commonly observed in the magnetosphere.

Kong, J. A.↗
NASA NTRS1987

Internal gravity waves in the meteor zone in the Tbilisi Region

The study of wave disturbances (WD) in the upper part of the meteor zone (90 to 110 km) was made in the Tbilisi region. Observations were conducted using three ionospheric vertical sounders located at the corners of a triangle spaced from each other at a distance of 50 km, a four azimuth electrophotometer by the method of space reception with a small distance and a recording unit. These disturbances are measured and the results are given.

Sharadze, Z. S.↗
NASA NTRS2019

Fully-polarimetric millimeter-wave spectrometers for measurement of Earth's magnetic field

Earth’s ionosphere responds dynamically over a wide range of temporal and spatial scales to changes in the magnetosphere and solar wind from above, and to neutral atmospheric dynamics from below. Determining the dynamics and coupling of Earth's magnetosphere, ionosphere, and atmosphere by vector magnetic field measurements at all altitudes is essential, as the field plays a major role in controlling the distribution of ionospheric plasma. It is difficult to measure the magnetic B-field, either locally or globally, at the altitudes of the upper mesosphere and lower thermosphere (UMLT) where the transfer of energy and momentum between the plasma and neutral components of the system occur. The 118-GHz imaging magnetometer will measure all four Stokes parameters as a function of frequency about the Zeeman-split center of the 118-GHz molecular oxygen line. We are developing an array of fully-polarimetric millimeterwave radiometer/spectrometers operating near 118 GHz. These low cost, low power, low mass polarimetric 118 GHz millimeter-wave array receivers do not require cooling to meet the sensitivity requirements. With digital spectrometers we will be able to integrate the complete end-to-end system. This work will enable a second generation small satellite mission with an off-nadir viewing instrument comprised of 120 such receivers (arranged so that each spot on the Earth is observed simultaneously by four receivers each) that will globally map the magnetic field in the mesosphere at 42-76 km altitude at a horizontal resolution ~100 km with 1-sigma error of 40-120 nT, in typical mesospheric temperature conditions.

Mannucci, Anthony↗
NASA NTRS1973

OGO-6 experiment F-03

The results obtained with the retarding potential analyzer on the OGO-6 satellite are discussed. The information obtained during the OGO-6 flight concerned the following subjects: (1) measurement of electron flux density in the plasmasphere, (2) latitudinal variations of ion temperature, (3) heating in the nighttime ionosphere by conjugate photoelectrons, (4) longitudinal variation in equatorial ion temperature at low altitude, and (5) identification of heavy ions in the upper F region.

Hanson, W. B.↗
NASA NTRS1979

Results of measurement of the night corpuscular flux on the MR-12 rockets in the JASPIC project (Soviet part of the program)

In June 1978, a joint Soviet-American project (JASPIC) was conducted, the goals of which were: (1) the study of the flows of spilling electrons which act upon the middle-latitude ionosphere under nocturnal conditions (nocturnal corpuscular source of ionization); and (2) the mutual comparison of procedures for recording corpuscular radiations in the upper atmosphere, using meteorological and geophysical rockets.

Avdyushin, S. I.↗
NASA NTRS1999

MOLA-derived Roughness Data Used to Predict Surface Scattering for Mars Subsurface Radar Sounding

The Mars Express orbiter, to be launched by the European Space Agency in 2003, will carry a low-frequency radar sounding instrument, MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding). The primary goal of MARSIS is to map the distribution of water, both solid and (if present) liquid, in the upper several km of the martian crust. Detecting discontinuities in the crust, such as an ice-water transition, presents many challenges for a Mars orbital radar sounder. One challenge that must be overcome is the presence of radar scattering (echoes) from the surface of Mars, expected to be detected by the sounder antennas at the same time as any echoes aris-ing from subsurface interfaces. As the transmitted spherical wavefront spreads within the crust of Mars,. it also interacts with surface topography at off-nadir positions, creating a "clutter" signal that can mask the subsurface echoes. The MARSIS instrument will utilize Doppler filtering to limit the off-nadir clutter in the along-track direction, and a nadir-null secondary antenna to identify strong off-nadir clutter from the cross-track direction. To evaluate the effects of off-nadir surface clutter and the capability of these schemes to reduce the clutter, it is necessary to predict the range of scattering behavior that may be expected from martian surface topography. In this paper, we utilize Mars Orbital Laser Altimeter (MOLA) data from the current Mars Global Surveyor mission to characterize the topographic roughness of a variety of martian terrain types, at scales relevant to the MARSIS clutter problem. Segments of MOLA altimetry profiles are reduced to the topographic parameters rms slope and fractal dimension, which then are used as inputs to a near-nadir radar scattering model to predict the strength of the clutter signal. Additional information is contained in the original extended abstract.

Plaut, J. J.↗
NASA NTRS1991

The use of transition heights for the representation of ion composition

Several characteristic transition heights can be found in ionospheric ion-composition profiles. These are the boundaries between the regions dominated by light ions, atomic oxygen ions, molecular ions, and cluster ions, respectively. Ion-composition modeling can benefit from the use of these transition heights. Special emphasis is given to the 'upper' transition height H sub T (light ions to atomic oxygen) and to the 'lower' transition height h sub t (atomic oxygen to molecular ions). Transition-height models deduced from rocket and satellite measurements are compared with the heights predicted by the International Reference Ionosphere. Considerable discrepancies are found between the different models as well as between the models and independent measurements.

Bilitza, Dieter↗