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Results for “Electron density”

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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Quasi-linear theory of electron density and temperature fluctuations with application to MHD generators and MPD arc thrusters.

Fluctuations in electron density and temperature coupled through Ohm's law are studied for an ionizable medium. The nonlinear effects are considered in the limit of a third order quasi-linear treatment. Equations are derived for the amplitude of the fluctuation. Conditions under which a steady state can exist in the presence of the fluctuation are examined and effective transport properties are determined. A comparison is made to previously considered second order theory. The effect of third order terms indicates the possibility of fluctuations existing in regions predicted stable by previous analysis.

Smith, J. M.↗
NASA NTRS1977

Development of far infrared attenuation to measure electron densities in cw pin discharge lasers

A two beam attenuation technique was devised to measure electron densities 10 to the 9th power to 10 to the 11th power cm/3 resolved to 1 cm, in a near atmospheric COFFEE laser discharge, using 496 micrometer and 1,220 micrometer radiations from CH3F, optically pumped by a CO2 laser. A far infrared generator was developed which was suitable except for a periodic intensity variation in FIR output deriving from frequency variation of the pump radiation.

Babcock, R. V.↗
NASA NTRS1978

Rocket observations of electron-density irregularities in the equatorial ionosphere below 200 km

Nike Apache rockets carring instrumentation to measure electron density and its fine structure in the equatorial ionosphere were launched from Chilca, Peru in May and June 1975. The fine structure experiment and the data reduction system are described. Results obtained from this system are presented and compared with those obtained by VHF radar and from other rocket studies. A description of the equatorial ionosphere and its features is also presented.

Klaus, D. E.↗
NASA NTRS1981

Electron densities for six planetary nebulae and HM SGE derived from the C 3 lambda 1907/1909 ratio

Electron densities for IC 418, NGC 6572, IC 1297, NGC 3242, NGC 6818, NGC 3211, and HM Sge derived from high dispersion IUE C III spectrograms are consistently higher than those derived from either surface brightness measurements of forbidden line intensity ratios in the visible. The nebulae were selected for a range of excitation classes from 3 to 9. Line splitting due to expansion velocities is observed for three objects. The great width of the lambda 1909 C III line in HM Sge suggests large expansion velocities.

Source record↗
NASA NTRS1990

New options for IRI electron density in the middle ionosphere

This paper reviews the present International Reference Ionosphere (IRI) model of electron density in the middle ionosphere and explores two new options for future editions of IRI. The first of these options is a better description of the bottomside thickness parameters, and the second is an analytical representation from E- to F2-peak using LAY-functions. For this analytical representation a table of standard parameters and constraints for the four LAY-functions recommended for IRI have been established.

Bilitza, Dieter↗
NASA NTRS1992

Sites of fine-scale electron density turbulence in the interstellar medium

Observations of radio-wave scattering effects probe interstellar electron-density turbulence. But with limited use of complementary data sets only broad conclusions have been obtained. The locations of this turbulence are unknown (phases, objects, etc.), as is the mechanism for its production, although it could play a role in various galactic processes. The IRAS data set was used to search for correlations between scattering and structures traced by infrared emitting dust. The existent HI (21-cm line emission), and 408-MHz radio-continuum all-sky surveys were used to search for correlations between scattering and structures traced by these emissions. Only lines of sight outside the galactic plane were considered (to better delimit the structures which might be causing scattering). No correlation is apparent between 21-cm line emission, or infrared continuum emission and interstellar scattering. However, a correlation exists between the scattering toward extragalactic radio sources and 408-MHz continuum emission.

Simonetti, John H.↗
NASA NTRS2004

A Correction for the IRI Topside Electron Density Model Based on Alouette/ISIS Topside Sounder Data

The topside segment of the International Reference Ionosphere (IRI) electron density model (and also of the Bent model) is based on the limited amount of topside data available at the time (40,OOO Alouette 1 profiles). Being established from such a small database it is therefore not surprising that the models have well-known shortcomings, for example, at high solar activities. Meanwhile a large data base of close to 200,000 topside profiles from Alouette 1,2, and ISIS I, 2 has become available online. A program of automated scaling and inversion of a large volume of digitized ionograms adds continuously to this data pool. We have used the currently available ISIs/Alouette topside profiles to evaluate the IRI topside model and to investigate ways of improving the model. The IRI model performs generally well at middle latitudes and shows discrepancies at low and high latitudes and these discrepancies are largest during high solar activity. In the upper topside IRI consistently overestimates the measurements. Based on averages of the data-model ratios we have established correction factors for the IRI model. These factors vary with altitude, modified dip latitude, and local time.

Bilitza, D.↗
NASA NTRS1979

Estimations of electron densities and temperatures in He-3 dominated plasmas

It is very useful to have a method of estimation for electron temperature and electron densities in nuclear pumped plasmas because measurements of such quantities are very difficult. This paper describes a method, based on rate equation analysis of the ionized species in the plasma and the electron energy balance. In addition to the ionized species, certain neutral species must also be calculated. Examples are given for pure helium and a mixture of helium and argon. In the HeAr case, He(+), He2(+), He/2 3S/, Ar(+), Ar2(+), and excited Ar are evaluated.

Depaola, B. D.↗
NASA NTRS2003

ISS FPP Ionospheric Electron Density and Temperature Measurements: Results, Comparison with the IRI-90 Model, and Implications for ISS Charging

We give measurement results of electron temperature and electron density from the Floating Potential Probe (FPP) on the International Space Station (ISS), and relate them to the electron current collection of the ISS solar arrays and the degree of charging of ISS when its Plasma Contacting Units (PCUs) are not operating. We show that on days of high solar activity index Kp, high levels of ISS charging are significantly more probable than on days of low solar activity, due to some abnormally low morning electron temperatures. Although the FPP electron temperatures measured are almost always higher than predicted by the International Reference Ionosphere 90 model (IRI-90), it is shown that the CHAMP satellite Langmuir Probe (PLP) also shows low dawn electron temperatures on the same day as those found by FPP. It is further shown that similar high levels of predicted charging, accompanied by vxB charging on the ISS structure, could exceed the -40 V specification on ISS charging, and could be dangerous to ISS astronauts if the PCUs fail to operate.

Ferguson, D. C.↗