Engineering topics

Chamberlain, J. W.

Publications and source records attributed to Chamberlain, J. W..

33 records · Page 2

NASA NTRS1976

Venus' night side ionosphere - Its origin and maintenance

A substantial nightside ionosphere has been observed on Venus by both Mariner 5 and Mariner 10. Major dayside ionic species such as O2(+) and other molecular ions have chemical lifetimes much shorter than the 244.3-day rotation period of the planet. Rapid transport of ions from the dayside to the nightside to the extent required seems most unlikely. Consequently, possibilities are investigated for local production of ions on the nightside itself. Constraints imposed by chemical lifetimes require atomic ions with low ionization potentials. It is suggested that metallic ions of meteoric origin are the positive charge carriers, and the plausibility of this mechanism is demonstrated. Other possibilities are examined and shown to be less likely. Meteor ablation on Venus, the aeronomy of metallic species, and the role of negative ions near the electron peaks of the atmosphere are discussed.

Butler, D. M.↗

NASA NTRS1976

Spectral line profiles for a planetary corona

The Lyman and Balmer emissions of a planetary corona depend on the exospheric temperature, the integrated column density of solar-illuminated hydrogen, and the region of phase space occupied by particles. Measurements of the intensity alone are incapable of defining the exosphere unambiguously. Line profiles with high spectral resolution can show whether a nonthermal component of the escaping hydrogen is present and can indicate at what altitude orbits of hydrogen atoms are depleted. It is necessary, however, to plan the observations carefully if they are to be fitted usefully to a model.

Chamberlain, J. W.↗

NASA NTRS1976

A mechanism for inducing climatic variations through ozone destruction: Screening of galactic cosmic rays by solar and terrestrial magnetic fields

A perturbation analysis, allowing for temperature and opacity feedbacks, is developed to calculate depletions in the O3 abundance and reductions of stratospheric solar heating that result from increases in NOx concentration. A pair of perturbation coefficients give the reduction in O3 and temperature through the stratosphere for a specified NOx increase. This type of analysis illustrates the tendency for various levels to self-heal when a perturbation occurs. Physical arguments indicate that the expected sign of the climatic effect is correct, with colder surface temperatures produced by reduced magnetic shielding. In addition, four qualitative reasons are suggested for thinking that significant ozone reductions by cosmic ray influxes will lead to an increased terrestrial albedo from stratospheric condensation. In this view, long-term (approximately 10,000 years) climatic changes have resulted from secular geomagnetic variations while shorter (approximately 100 years) excursions are related to changes in solar activity.

Chamberlain, J. W.↗

NASA NTRS1975

Venus' spectroscopic phase variation - Implications of the Mariner 10 photographs

The recent ultraviolet photographs of Venus by Mariner 10 have shown an irregular cloud structure. There is an apparent tendency for clearing along a wide equatorial band more or less centered on the subsolar point. This synoptic picture is in marked contrast to the uniform cloud cover conventionally used in model calculations of the variation with phase of CO2 absorption bands. To illustrate the consequences of subsolar weakening of CO2 absorption, a mathematically simple (but realistically naive) model is used. Two conclusions are reached: (1) efforts to distinguish between single- and double-layer models for the clouds from spectroscopic data alone are not merely ambiguous (as argued earlier by Chamberlain and Smith); with present data they are hopeless; (2) the decrease in the CO2 absorption close to full phase, as reported by Young et al., could result entirely from an equatorial darkening that is relatively inconsequential at the crescent phase and increasingly predominant for fuller phases.

Chamberlain, J. W.↗

NASA NTRS1975

Planetary spectra for anisotropic scattering

Some of the effects on planetary spectra that would be produced by departures from isotropic scattering are examined. The phase function is the simplest departure to handle analytically and the only phase function, other than the isotropic one, that can be incorporated into a Chandrasekhar first approximation. This approach has the advantage of illustrating trends resulting from anisotropies while retaining the simplicity that yields physical insight. An algebraic solution to the two sets of anisotropic H functions is developed in the appendix. It is readily adaptable to progammable desk calculators and gives emergent intensities accurate to 0.3 percent, which is sufficient even for spectroscopic analysis.

Chamberlain, J. W.↗

NASA NTRS1975

Spectral line profiles for a planetary corona

The Lyman and Balmer emission of a planetary corona depend on the exospheric temperature, the integrated column density of solar-illuminated hydrogen, and the region of phase space occupied by particles. Measurements of the intensity alone are incapable of defining the exosphere unambiguously. Line profiles, with high spectral resolution, can show whether a nonthermal component of the escaping hydrogen is present, and can indicate at what altitude satellite orbits of hydrogen atoms are depleted.

Chamberlain, J. W.↗

NASA NTRS1965