Engineering topics

Maier, E. J.

Publications and source records attributed to Maier, E. J..

31 records · Page 2

NASA NTRS1973

The angular distribution of ion flux around an ionospheric satellite.

Ion measurements from the Explorer 31 satellite were used to determine the angular distribution of ions around the satellite. The ion distributions were compared with the electron distributions measured on the same satellite. It is shown that the electron currents (fluxes) in the wake are always larger than the ion currents for a wide domain of plasma parameters. A quantitative comparison of the ion fluxes with a neutral approximation model for the angular distribution is considered. It is found that the ion fluxes become progressively larger than the corresponding computed neutral fluxes as the angle of attack increases from 0 to 180 deg.

Samir, U.↗

NASA NTRS1973

The effect of grid transparency and finite collector size on determining ion temperature and density by the retarding potential analyzer

The analysis of ion data from retarding potential analyzers (RPA's) is generally done under the planar approximation, which assumes that the grid transparency is constant with angle of incidence and that all ions reaching the plane of the collectors are collected. These approximations are not valid for situations in which the ion thermal velocity is comparable to the vehicle velocity, causing ions to enter the RPA with high average transverse velocity. To investigate these effects, the current-voltage curves for H+ at 4000 K were calculated, taking into account the finite collector size and the variation of grid transparency with angle. These curves are then analyzed under the planar approximation. The results show that only small errors in temperature and density are introduced for an RPA with typical dimensions; and that even when the density error is substantial for non-typical dimensions, the temperature error remains minimal.

Troy, B. E., Jr.↗

NASA NTRS1972

Photoelectron escape fluxes over the equatorial and midlatitude regions

Satellite measurements of photoelectron escape flux around noontime made by Explorer 31 in 600-800 km altitude range are reported for the equatorial and midlatitude regions. The pitch angle distributions and the spectral distributions are derived from the data. Analyzed data show that the flux for equatorial regions is lower by a factor 2 to 3 in comparison to that of midlatitude regions. Theoretical calculations are also made to compare with observed escape fluxes.

Narasingarao, B. C.↗

NASA NTRS1972

Rocket measurements of conjugate photoelectrons during the total solar eclipse of 7 March 1970 over Wallops Island.

Results of measurements made with a retarding potential analyzer on a Nike-Tomahawk rocket during the totality of the solar eclipse, showing definite evidence for the existence of photoelectrons from the conjugate hemisphere. Photoelectrons are observed in the altitude range from 120 to 260 km. The observed flux in the energy range from 2 to 30 eV is relatively constant above about 200 km, but decreased below that altitude. The flux of 5-eV energy electrons above 200 km altitude is about 10 to the 7th power electrons/cm/sec/eV. Higher-energy electrons were also observed, and it is possible that the energy content of these observed fluxes of conjugate-point photoelectrons is sufficient to maintain the observed electron densities and temperatures during the total eclipse.

Maier, E. J.↗

NASA NTRS1972

The upper atmosphere as a regulator of subauroral red arcs.

The mechanisms for producing a subauroral red arc (SARARC) are studied by solving a system of basic ionospheric and atmospheric equations. It is shown that many of the observed features of a SARARC can be explained within the framework of the two processes generally responsible for the ionospheric behavior during a magnetic storm: (1) energy conduction from the magnetosphere to the ionosphere and (2) the changes in neutral composition of the lower atmosphere caused by the increase in turbulent mixing. Both processes trigger a complex chain of events which ultimately results in the redistribution of both the charged and neutral particles, an increase in the electron, ion, and neutral temperatures, and a decrease in the electron density in the altitude region near the F2 peak. It is shown that both the occurrence and the emission intensity of a SARARC are regulated by the neutral atmosphere, even though conduction of the thermal energy from the magnetosphere to the ionosphere provides the excitation energy of the optical remission.

Chandra, S.↗

NASA NTRS1971