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Almeida, O. G.

Publications and source records attributed to Almeida, O. G..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Protonospheric columnar electron content determination. II - Observations

The results of over 300 hours of measurements of the quantity I sub w - the difference between total columnar electron content, derived from the differential phase-path data, and Faraday electron content - is presented. The interpretation of the measurements in terms of protonospheric content is discussed in the light of a previous analysis which demonstrates that good protonospheric content measurements can only be obtained under certain geometries of observations unless information on the shape and height of the ionospheric layer is available. A strong correlation between I sub w and the ionospheric content is observed in most of the Arecibo data, because they were collected under unfavorable conditions. The Stanford data, on the other hand, yield good measurements of the protonospheric content. The May 1969 observations show a strong depletion of protonospheric content during a magnetic storm and its subsequent recovery. This is in general agreement with flux tube content behavior observed by the whistler technique during similar conditions.

Almeida, O. G.↗
NASA NTRS1973

Protonospheric columnar electron content determination. I - Analysis.

A combination of phase-path length difference and Faraday rotation angle data obtained from geostationary satellite transmissions is used to determine the integration constant necessary to convert phase-path length difference information into absolute values of total slant columnar electron content. The total content thus determined, which is the sum of the ionospheric and protonospheric contents, is measured with uncertainties about one order of magnitude smaller than the value of the protonospheric content. It is thus, in principle, possible to determine the latter by subtracting from the measurement the so-called 'Faraday content.' This idea, proposed by several authors in the past, is critically examined in the present paper. It is impossible to totally eliminate the ionospheric contribution to the measurements; however, it is shown that the degree of elimination depends on the type of distribution of the longitudinal component of the geomagnetic field along the path of observation. Satisfactory minimization of the ionospheric contribution can be accomplished only under certain geometries of observation.

Almeida, O. G.↗
NASA NTRS1972

VHF/UHF technique for the determination of the columnar electron contents of the plasmasphere and of the protonosphere using geostationary satellite transmission: Observations during magnetic storms

Measurements of the total electron content of the plasmasphere up to geostationary heights were made using the beacon transmitters aboard the satellite ATS-3. The technique employed is a combination of the phase-path length difference and the Faraday rotation angle methods. Such a combination permits very accurate determination of the integration constant necessary to convert phase-path length difference data into information about the absolute value of the columnar content.

Almeida, O. G.↗
NASA NTRS1972

Neutral winds implied by electron content observations during the 7 March 1970 solar eclipse.

Measurements of columnar electron content using geostationary satellite signals were made at several of our observatories throughout the U.S., during the 7 March 1970 solar eclipse. The ionospheric response to the solar eclipse was simulated in a computer. Discrepancies between observed and simulated electron content behaviors can be greatly reduced by assuming the existence of plausible neutral winds originated by the eclipse in the F-region heights.

Almeida, O. G.↗