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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 127 records · Page 7
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NASA NTRS1984

The dayside Venus ionosphere. II - Combined numerical model of ion and neutral composition above 120 km

The median vertical profile of ion densities for the dayside Venusian ionosphere obtained by the orbiter retarding potential analyzer (ORPA) is simulated by one-dimensional model calculations. The model includes both neutral and ionic chemistry, eddy and molecular diffusion for neutral constituents, and ion-plasma diffusion for ionic constituents. The electron and ion temperatures measured by the ORPA are used to calculate the plasma diffusion coefficients and scale heights for ions. The predicted O2(+) densities below about 200 km agree particularly well with observations by the ORPA, but the model values are significantly less than those measured by the orbiter ion mass spectrometer. The observed ion composition is interpreted in terms of densities of the neutral atmosphere and its composition.

Shimazaki, T.↗
NASA NTRS1983

Aeronomy of the inner planets

Recent progress concerning the thermospheres of Venus and Mars is reviewed in this report. A dramatic advance in our understanding of the upper atmosphere and ionosphere of Venus has occurred during the 1979-82 quadrennium, and was primarily due to the large amount of data generated by the Pioneer Venus mission. Progress on Mars has been rather modest and has stemmed from theoretical modeling efforts related to the 1976 Viking observations. This report covers the following topics: the thermosphere and ionosphere of Mars, the thermosphere of Venus, some aspects of the solar wind-ionosphere interaction of Venus, the dayside ionosphere of Venus including both composition and energetics, and the nightside ionosphere of Venus.

Cravens, T. E.↗
NASA NTRS2003

Low Earth Orbit Plasma Variability Model

The empirical International Reference Ionosphere is a widely used model for estimating low Earth orbit plasma characteristics for use in spacecraft design and mission analysis. The climatological model provides mean values of plasma density, temperature, composition, and other ionospheric parameters that can be used to estimate the average magnitude of spacecraft charging, current collection for electrodynamic tethers, and other effects on spacecraft design. Mean IRI parameters are not adequate to answer questions such as what is the maximum or minimum value of the spacecraft potential, does the maximum spacecraft potential exceed a program requirement, will an electrodynamic tether provide adequate drag to deorbit a satellite at end of life, and will the tether provide sufficient thrust to reboost a spacecraft at any time in the solar cycle. These questions require estimates of the variability of the ionospheric environment about the mean values. This presentation describes the status of work at MSFC to develop an empirical ionospheric variability model that can be used in conjunction with the climatological IRI model to provide both mean ionospheric parameters and variations of the environment about the mean. Our technique will use an extensive database of satellite and radar observations of the electron density and temperature to derive variances of the data about the model values. The variances will then be incorporated into Fortran wrapper software that calls the IRI-2001 model and provides statistical estimates of the deviation of the environment about the mean IRI values. We will provide an update on the state of the database development and provide examples of analysis and modeling efforts completed specifically for an International Space Station application.

Minow, Joseph I.↗
NASA NTRS1993

International Reference Ionosphere: Past, present, and future. I - Electron density. II - Plasma temperatures, ion composition and ion drift

The most important investigations leading to the International Reference Ionosphere 1990 (IRI-90) are overviewed, and the latest version of the model is described. The shortcomings and limitations of the IRI-90 are pointed out, together with the ways of overcoming them. The list of studies that the IRI group has yet to carry out includes the investigations of magnetic storm effects as the highest priority. This paper discusses determinations of and the available data on the electron density, plasma temperatures, ion composition, and ion drift in the ionosphere, together with future improvements needed on these parameters.

Bilitza, D.↗
NASA NTRS1972

Metallic ions in the equatorial ionosphere

Four positive ion composition measurements of the equatorial E region made at Thumba, India, are presented. During the day, the major ions between 90 and 125 km are NO(+) and O2(+). A metallic ion layer centered at 92 km is observed, and found to contain Mg(+), Fe(+), Ca(+), K(+), Al(+), and Na(+) ions. The layer is explained in terms of a similarly shaped latitude distribution of neutral atoms which are photoionized and charge-exchanged with NO(+) and O2(+). Three body reactions form molecular metallic ions which are rapidly lost by dissociative ion-electron recombination. Nighttime observations show downward drifting of the metallic ion layer caused by equatorial dynamo effects. These ions react and form neutral metals which exchange charges with NO(+) and O2(+) to produce an observed depletion of those ions within the metallic ion region.

Aikin, A. C.↗
NASA NTRS1973

Metallic ions in the equatorial ionosphere.

Four positive ion composition measurements of the equatorial E region at Thumba, India, are presented. During the day, the major ions between 90 and 125 km are NO+ and O2+. The relative concentrations are similar to those observed at midlatitudes but exhibit unusual structural behavior with altitude. A metallic ion layer centered at 92 km is found to contain Mg+, Fe+, Ca+, K+, Al+, Na+, and possibly Si+ ions. The layer is explained in terms of a similarly shaped altitude distribution of neutral atoms that are photoionized and charge exchanged with NO+ and O2+. Three-body reactions form molecular metallic ions that are rapidly lost by dissociative ion-electron recombination.

Aikin, A. C.↗
NASA NTRS1991

The structure of the Venus ionosphere

The morphology and temporal variability of the Venus ionosphere are characterized, reviewing the results of recent theoretical investigations, observations, and in situ measurements, especially by the Pioneer Venus Orbiter (PVO). Consideration is given to the Pioneer mission and orbit evolution, early radio occultation profiles of ionospheric N(e), the mean structure and thermal balance of the ionosphere, the ion composition and its dawn-dusk asymmetry, the small-scale spatial structure on the nightside, latitudinal and seasonal variations, solar-cycle effects, suprathermal electrons and superthermal ions, and the global configuration and stability of the ionopause. Data from a single PVO passage through the ionotail are discussed in detail, examining the implications for ion escape and the solar-cycle and short-term variability. The differences among the terrestrial, Martian, and Venusian ionospheres are outlined; the PVO data base is described; and the sources of measurement error are indicated.

Brace, L. H.↗
NASA NTRS1981

Dynamic variations observed in thermal and superthermal ion distributions in the dayside ionosphere of Venus

In-situ measurements of the ion composition and concentration of the ionosphere of Venus are obtained with the Bennett RF ion mass spectrometer (OIMS) on the Pioneer Venus Orbiter (PVO). Dayside ion profiles exhibit considerable variability in the height of the ionopause as well as the scale heights of the ion constituents, which reflect the compression and expansion of the ionosphere in response to solar wind variations. Near the dayside upper boundary of the thermal O+ distribution, super-thermal ions are detected by the OIMS, presenting a complication for identifying the ion signature of the ionopause. Correlated with the presence of the superthermal ions, the ac electric field detector (OEFD) detects regions of intensified signals, with peak response in the 100 Hz frequency channel. It is expected that further analysis of the superthermal ion-electric field signatures will contribute to a clearer understanding of the physical processes underlying the formation of the ionopause.

Taylor, H. A., Jr.↗
NASA NTRS1986

The ionosphere of Uranus - A myriad of possibilities

A one-dimensional model has been used to study the effects of exospheric temperature, methane and water influx, ionospheric outflow, and electron precipitation on the composition and structure of the ionosphere of Uranus. Peak ion concentrations range from 1000 to 1 million per cu cm with a wide variation in peak altitude, which depends strongly on the exospheric temperature. In all the cases considered, H(+) is the major ion in the topside ionosphere. At altitudes near or below the peak, H3(+) and CH5(+) can dominate, depending on the magnitude of CH4 and H2O influx. Atomic hydrogen column depths above the methane absorbing layer exceed 10 to the 17th per sq cm and can produce large (400 R) emissions of resonantly scattered Lyman-alpha. In the sunlit polar cap, electron precipitation with energy fluxes of 0.6 to 1.0 erg/sq cm s results in direct production of Lyman-alpha emissions that exceed 1 kR.

Chandler, M. O.↗
NASA NTRS1964

Ionosphere

Electron density and temperature, ion composition and density, and effects of solar corpuscular radiation in ionosphere - satellite drag measurements

ELECTRON TEMPERATURE↗
NASA NTRS1966

The constitution of the topside ionosphere.

Topside ionosphere constitution, examining electron and ion distribution, charged particle scale height, ion composition, electron and ion temperatures and magnetosphere

IONOSPHERIC COMPOSITION↗
NASA NTRS1985

Positive ion composition and derived particle heating in the lower auroral ionosphere

Two E11a rocket flights in salvo B (launched on November 16, 1980) and A2 (launched on November 30, 1980), which provide positive ion composition, total and partial ion density, and electron density in the altitude range 60-170 km above Kiruna under conditions of moderate and strong magnetic disturbance, are examined. It is shown that the ionization sources are predominantly precipitating electrons in salvo B and precipitating protons in salvo A2. Under winter-time auroral conditions the characteristics of the positive ion composition are large NO(+)/O2(+) density ratios, with maximum values of 20 at 118 km in salvo B and 100 at 100 km in salvo A2, respectively. The transition from NO(+) to proton hydrates is found at an altitude of 79 km in salvo B and 76 km in salvo A2. The calculated O(+) and N(+) densities are in good agreement with model calculations and from these calculations it is concluded that 28(+) is mainly N2(+) above 110 km in salvo B and above 105 km in salvo A2, and Si(+) below these altitudes. By altitude integration of the ion-electron pair production, the energy flux of precipitating particles is found to have values of 0.85 mW/sq m and 1.0 mW/sq m in salvoes B and A2, respectively.

Kopp, E.↗
NASA NTRS1973

Measurements of VLF polarization and wave normal direction on OGO-F

A major achievement of the F-24 experiment on OGO 6 was a verification of the theory of the polarization of proton whistlers. As predicted, the electron whistler was found to be right-hand polarized and the proton whistler left hand polarized. The transition from right- to left-hand polarization was found to occur very rapidly. Thus it appears that the experimental technique may allow great accuracy in the measurement of the cross-over frequency, a frequency that provides information on the ionic composition of the ionosphere.

Helliwell, R. A.↗
NASA NTRS1974

High latitude minor ion enhancements - A clue for studies of magnetosphere-atmosphere coupling

An investigation is conducted of upper ionosphere molecular ion composition data, which because of the unexpected, abrupt enhancements sometimes exhibited at high latitudes, may indirectly offer additional clues to understanding the processes by which the lower atmosphere becomes perturbed. It is found that molecular ion irregularities are sometimes localized in a relatively narrow region of time and space. The abruptness of these events suggests that lower atmosphere energetic processes presumed responsible for the ion enhancements may also be narrowly distributed.

Taylor, H. A., Jr.↗
NASA NTRS2010

A Perspective of the Science and Mission Challenges in Aeronomy

There are significant fundamental problems for which aeronomy can provide solutions and a critical role in applied science and space weather that only aeronomy can address. Examples of unresolved problems include the interaction of neutral and charged, the role of mass and energy transfer across Earth's interface with space, and the predictability of ionospheric density and composition variability. These and other problems impact the productivity of space assets and thus have a tangible applied dimension. This talk will explore open science problems and barriers to potential mission solutions in an era of constrained resources.

Spann, James F.↗
NASA NTRS1979

Venus ionosphere - Photochemical and thermal diffusion control of ion composition

The major photochemical sources and sinks for ten of the ions measured by the ion mass spectrometer on the Pioneer Venus bus and orbiter spacecraft that are consistent with the neutral gas composition measured on the same spacecraft are identified. The neutral gas temperature (as a function of solar zenith angle) derived from measured ion distributions in photochemical equilibrium is given. Above 200 kilometers, the altitude behavior of ions is generally controlled by plasma diffusion, with important modifications for minor ions due to thermal diffusion resulting from the observed gradients of plasma temperatures. The dayside equilibrium distributions of ions are sometimes perturbed by plasma convection, while lateral transport of ions from the dayside seems to be a major source of the nightside ionosphere.

Bauer, S. J.↗