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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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NASA NTRS1988

Ionosphere-thermosphere momentum coupling at solar maximum and solar minimum from DE-2 and AE-C data

DE-2 and AE-C measurements of plasma and neutral densities were used to derive time constants for momentum transfer (MT) to neutrals from ions in the high-latitude thermosphere. The MT time constants for solar cycle maximum (DE-2) and for solar cycle minimum (AE-C) were averaged and binned according to geomagnetic latitude and LT to provide a quantitative measure for the tightness of ion-neutral momentum coupling (MC) in the 250-350-km altitude range. Comparisons with results obtained using the Chiu and MSIS-83 empirical models have provided an indication of the accuracy with which thermospheric general circulation models quantitatively reproduce the MC between ions and neutrals in the high-latitude F-region.

Ponthieu, J. J.↗

NASA NTRS1988

An analysis of satellite observations of the O I EUV dayglow

Observations of the latitudinal variation of the 1356-A, 1304-A, and 989-A O I earth dayglow, obtained with the USAF STP78-1 satellite at solar maximum on March 21, 1979, are reported and compared with the predictions of thermospheric models and published laboratory measurements of electron-impact excitation cross sections. The results are presented in extensive tables and graphs and characterized in detail, with particular attention to the 1304-A solar flux and the 989-A branching ratio. The STP78-1 data (as well as simultaneous AE-E satellite measurements ) are shown to indicate exospheric temperatures that were 220-240-K higher, but varied significantly less with latitude, than those predicted by the MSIS-83 model (Hedin, 1983) for the day of the observations.

Link, R.↗

NASA NTRS1988

Empirical global model of upper thermosphere winds based on atmosphere and dynamics explorer satellite data

Thermospheric wind data obtained from the Atmosphere Explorer E and Dynamics Explorer 2 satellites have been used to generate an empirical wind model for the upper thermosphere, analogous to the MSIS model for temperature and density, using a limited set of vector spherical harmonics. The model is limited to above approximately 220 km where the data coverage is best and wind variations with height are reduced by viscosity. The data base is not adequate to detect solar cycle (F10.7) effects at this time but does include magnetic activity effects. Mid- and low-latitude data are reproduced quite well by the model and compare favorably with published ground-based results. The polar vortices are present, but not to full detail.

Hedin, A. E.↗

NASA NTRS1989

The behavior of the electron density and temperatue at Millstone Hill during the equinox transition study September 1984

The ionospheric electron density and temperature variations is simulated during the equinox transition study in September 1984 and the results are compared with measurements made at Millstone Hill. The agreement between the modeled and measured electron density and temperature for the quiet day (18 September) is very good but there are large differences on the day of the storm (19 September). On the storm day, the measured electron density decreases by a factor of 1.7 over the previous day, while the model density actually increases slightly. The model failure is attributed to an inadequate increase in the ratio of atomic oxygen to molecular neutral densities in the MSIS neutral atmosphere model, for this particular storm. A factor of 3 to 5 increase in the molecular to atomic oxygen density ratio at 300 km is needed to explain the observed decrease in electron density. The effect of vibrationally excited N sub 2 on the electron density were studied and found to be small.

Richards, P. G.↗

NASA NTRS1988

A reanalysis of rocket measurements of the ultraviolet dayglow

Rocket measurements of O I 989, 1304, 1356 A and N2 Lyman-Birge-Hopfield band emission in the midlatitude dayglow reported by Gentieu et al. (1979) and Eastes et al. (1985) are reexamined. MSIS-83 atomic oxygen densities, the 1304 and 1356 A excitation cross sections of Zipf and Erdman (1985), and SMM solar 1304 A irradiance measurements are consistent with the observed O I and N2 emission intensities. Atmosphere Explorer E (AE-E) measurements of the solar EUV irradiance near solar maximum are consistent with the 1980 rocket airglow data, but the solar EUV irradiance required to explain the 1978 airglow data is a factor of 1.5 larger than indicated by AE-E. Enhancement of the 1304 A excitation cross section due to radiative entrapment of cascade-feeding photons is much less than the factor of two predicted by the cascade model of Julienne and Davis (1976).

Link, R.↗

NASA NTRS1989

The behavior of the electron density and temperature at Millstone Hill during the equinox transition study September 1984

Richards, P. G.↗

NASA NTRS1990

The EUV dayglow at high spectral resolution

Rocket observations and spectra of the dayglow spectrum of the terrestrial atmosphere between 840 and 1860 A are studied. Three bands of the N2 c-prime 4 system are seen clearly resolved in the dayglow. Analysis of high-resolution N2 Lyman-Birge-Hopfield data shows no anomalous vibrational distribution as has been reported from other observations. Altitude profiles of the observed O and N2 emissions demonstrate that the MSIS-83 model O and N2 densities are appropriate for the conditions of the rocket flights.

Morrison, M. D.↗

NASA NTRS1990

Low-latitude thermospheric neutral winds determined from AE-E measurements of the 6300-A nightglow at solar maximum

Atmosphere Explorer E (AE-E) measurements of the O(1D) 6300-A emission in the nighttime equatorial thermosphere are used to infer the height of the F2 layer peak as a function of latitude and local time. The investigation is conducted both for northern hemisphere winter solstice and for spring equinox, under solar maximum conditions. The layer heights are used to derive magnetic meridional components of the transequatorial neutral wind, in conjunction with the MSIS-86 model and previous Jicamarca incoherent scatter measurements of the zonal electric field. The AE-E wind estimates indicate a predominant summer to winter flow for the winter solstice case. Comparisons are made with the empirical horizontal wind model HWM87 and with winds generated by the thermospheric general circulation model. The model predictions and experimental results are generally in good agreement, confirming the applicability of visible airglow data to studies of the global neutral wind pattern.

Burrage, M. D.↗

NASA NTRS1990

Plasma density enhancements created by the ionization of the Earth's upper atmosphere by artificial electron beams

Analytical calculations and experimental observations relating to the interaction with the Earth's upper atmosphere of electron beams emitted from low altitude spacecraft are presented. The problem is described by two coupled nonlinear differential equations in the up-going (along a magnetic field line) and down-going differential energy flux. The equations are solved numerically, using the MSIS atmospheric model and the IRI ionospheric model. The results form the model compare well with recent observations from the CHARGE 2 sounding rocket experiment. Two aspects of the beam-neutral atmosphere interaction are discussed. First, the limits on the electron beam current that can be emitted from a spacecraft without substantial spacecraft charging are investigated. This is important because the charging of the spacecraft to positive potentials limits the current and the escape energy of the beam electrons and thereby limits the ionization of the neutral atmosphere. As an example, we find from CHARGE 2 observations and from the model calculations that below about 180 km, secondary electrons generated through the ionization of the neutral atmosphere by 1 to 10 keV electron beams from sounding rockets, completely balance the beam current, thereby allowing the emission of very high beam currents. Second, the amount of plasma production in the beam-streak is discussed. Results are shown for selected values of the beam energy, spacecraft velocity, and spacecraft altitude.

Neubert, Torsten↗

NASA NTRS1989

Proposed reference models for atomic oxygen in the terrestrial atmosphere

A provisional Atomic Oxygen Reference model was derived from average monthly ozone profiles and the MSIS-86 reference model atmosphere. The concentrations are presented in tabular form for the altitude range 40 to 130 km.

Llewellyn, E. J.↗

NASA NTRS1991

The measurement of atomic oxygen in the mesosphere and lower thermosphere

A discussion of the laboratory calibration, calibration simulation, and accuracy of a resonance fluorescence instrument for measuring oxygen atoms is presented. The discussion demonstrates that a sensor can be calibrated with good accuracy to obtain in situ measurements of the oxygen density in the mesosphere/lower thermosphere. Oxygen data are reported from six rocket flights. These data represent four midlatitude flights and two auroral flights. There are two night and two day profiles for the midlatitude experiments. The maximum densities found from these sets of data in the 90-100 km regions are between 1.5 x 10 to the 11th/cu cm and 3.5 x 10 to the 11th/cu cm. Agreement with the MSIS-86 model predictions is obtained for altitudes above 120 km for midlatitude flights. The auroral data are less than the model prediction by about a factor of 2. The data show structure that is probably indicative of gravity wave effects of a nominal 5-km vertical wavelength.

Sharp, William E.↗

NASA NTRS1992

Comparison of the USU ionospheric model with the UCL-Sheffield coupled thermospheric-ionospheric model

Several physical models of the high-latitude ionosphere have been developed that describe the time-dependent evolution of the E- and F-region plasma density. The models require a variety of inputs, including solar EUV fluxes, magnetospheric convection, auroral precipitation, and neutral atmosphere. Of specific relevance to this study is how the neutral atmosphere is incorporated into the ionospheric models. For the USU ionospheric model, the neutral atmosphere is the MSIS 1986 empirical model, while for the UCL-Sheffield coupled thermospheric-ionospheric model the neutral atmosphere is computed simultaneously with the ionosphere. Both models were run for similar solar and magnetospheric conditions (solar maximum, moderate geomagnetic activity, and winter solstice). Solar maximum conditions ensured a strong coupling between the ionosphere and thermosphere, which provided the possibility of a large ionospheric difference between the two physical models. This was further enhanced by choosing winter conditions so that the densities were not dominated by sunlight. The comparison of the two models indicated that both models predict the same morphological features with similar ionospheric densities, generally within about 30 percent.

Sojka, J. J.↗

NASA NTRS1992

Helium in the polar wind

The coupled time-dependent continuity, momentum, and energy equations for four charged species (H(+), He(+), O(+) and electrons) moving through a stationary upper neutral atmosphere (composed of O2, N2, O, He, and H) were solved along open geomagnetic field lines using a modified version of the Gombosi et al. (1985) model. The thermospheric densities and temperatures, obtained from the MSIS-86 model (Hedin, 1987), were used to calculate neutral-ion sources, sinks, and collision frequencies. The various cross sections and conductivities employed by the Gombosi et al. model were also updated. The paper presents the first time-dependent solutions for the He(+) component of the polar wind. Special attention is paid to the solar cycle variation of the ion upflows.

Gombosi, T. I.↗

NASA NTRS1993

Evaluation of hole sizes in structures requiring EVA services as a means to prevent gloved-hand finger entrapment

One of the concerns of Space Station designers was making sure that the suited crewmembers' gloved fingers are not trapped in the holes that may be present in the structures during EVA activities. A study was conducted on 11 subjects to determine the minimum and maximum possible hole sizes that would eliminate the possibility of finger entrapment. Subjects wore pressurized gloves and attempted to insert their fingers into holes of various sizes. Based on the experimental results, it is recommended that the smallest diameter should be less than 13.0 mm and the largest diameter should be greater than 35.0 mm in order to eliminate the possibility of finger entrapment while wearing gloves. It is also recommended that the current requirements specified by the MSIS-STD-3000 (Section 6.3.3.4) should be modified accordingly.

Rajulu, Sudhakar L.↗

NASA NTRS1991

Assured crew return vehicle man-systems integration standards

This is Volume 6 of the Man-Systems Integration Standards (MSIS) family of documents, which is contained in several volumes and a relational database. Each volume has a specific purpose, and each has been assembled from the data contained in the relational database. Volume 6 serves as the Assured Crew Return Vehicle project man-systems integration design requirements. The data in this document is a subset of the data found in Volume 1 and defines the requirements which are pertinent to the Assured Crew Return Vehicle as defined in the SPRD. Additional data and guidelines are provided to assist in the design.

Source record↗

NASA NTRS1992

Helium escape from the Earth's atmosphere - The charge exchange mechanism revisited

We have studied the escape of neutral helium from the terrestrial atmosphere through exothermic charge exchange reactions between He(+) ions and the major atmospheric constituents N2, O2 and O. Elastic collisions with the neutral background particles were treated quantitatively using a recently developed kinetic theory approach. An interhemispheric plasma transport model was employed to provide a global distribution of He(+) ions as a function of altitude, latitude and local solar time and for different levels of solar ionization. Combining these ion densities with neutral densities from an MSIS model and best estimates for the reaction rate coefficients of the charge exchange reactions, we computed the global distribution of the neutral He escape flux. The escape rates show large diurnal and latitudinal variations, while the global average does not vary by more than a factor of three over a solar cycle. We find that this escape mechanism is potentially important for the overall balance of helium in the Earth's atmosphere. However, more accurate values for the reaction rate coefficients of the charge exchange reactions are required to make a definitive assessment of its importance.

Lie-Svendsen, O.↗

NASA NTRS1993

A model for generating UV images at satellite altitudes

Vertical perspective, mercator, and tilted perspective projection images are presented which contain calculated dayglow, nightglow, and aurora. These images are discussed in terms of their structure's sources, which encompass composition variations, solar zenith angle changes, and changes in the path length experienced on going from disk-viewing to limb-viewing. Both a global thermospheric model (MSIS-86) and a global ionospheric model (the International Reference Ionosphere) are used to respectively specify neutral composition and the profiles of OI and OII.

Cox, R. J.↗

NASA NTRS1993

Prediction of three sigma maximum dispersed density for aerospace applications

Free molecular heating (FMH) is caused by the transfer of energy during collisions between the upper atmosphere molecules and a space vehicle. The dispersed free molecular heating on a surface is an important constraint for space vehicle thermal analyses since it can be a significant source of heating. To reduce FMH to a spacecraft, the parking orbit is often designed to a higher altitude at the expense of payload capability. Dispersed FMH is a function of both space vehicle velocity and atmospheric density, however, the space vehicle velocity variations are insignificant when compared to the atmospheric density variations. The density of the upper atmosphere molecules is a function of altitude, but also varies with other environmental factors, such as solar activity, geomagnetic activity, location, and time. A method has been developed to predict three sigma maximum dispersed density for up to 15 years into the future. This method uses a state-of-the-art atmospheric density code, MSIS 86, along with 50 years of solar data, NASA and NOAA solar activity predictions for the next 15 years, and an Aerospace Corporation correlation to account for density code inaccuracies to generate dispersed maximum density ratios denoted as 'K-factors'. The calculated K-factors can be used on a mission unique basis to calculate dispersed density, and hence dispersed free molecular heating rates. These more accurate K-factors can allow lower parking orbit altitudes, resulting in increased payload capability.

Charles, Terri L.↗