Second species solutions with an 0(μ v ), 0<v<1, near-Moon passage

This paper illustrates the application of the theory for second species solutions with an 0( ^v ), 0<v<1, near-Moon passage to first species-second species bifurcations and to second species-second species bifurcations. It also corrects and improves the asymptotic approximations obtained in the author's previous work on this subject and it establishes a local form of Broucke's Principle for the types of bifurcations studied in this paper.This work was supported by the National Science Foundation under Grant MCS 7703591.     

Radius of convergence of Lie series for some elliptic elements

For equatorial orbits about an oblate body, we show that the Lie series for the elliptic elementse,f,l and diverge when the oblateness exceeds a critical multiple of the transformed eccentricity constant. The use of similar truncated series expansions for such elliptic elements by Brouwer accounts for the first-order errors at low eccentricity in his derived coordinates for an artificial satellite.     

A survey of coronal holes and their solar wind associations throughout sunspot cycle 20

To gain insight into the relationships between solar activity, the occurrence and variability of coronal holes, and the association of such holes with solar wind features such as high-velocity streams, a study of the period 1963–1974 was made. This period corresponds approximately with sunspot cycle 20. The primary data used for this work consisted of X-ray and XUV solar images obtained from rockets. The investigation revealed that:

1. The polar coronal holes prominent at solar minimum, decreased in area as solar activity increased and were small or absent at maximum phase. This evolution exhibited the same phase difference between the two hemispheres that was observed in other indicators of activity.
2. During maximum, coronal holes occurred poleward of the sunspot belts and in the equatorial region between them. The observed equatorial holes were small and persisted for one or two solar rotations only; some high latitude holes had lifetimes exceeding two solar rotations.
3. During 1963–74 whenever XUV or X-ray images were available, nearly all recurrent solar wind streams of speed ?500 km s^?1 were found associated with coronal holes at less than 40° latitude; however some coronal holes appeared to have no associated wind streams at the Earth.

     

TheF N method for solving radiative-transfer problems in plane geometry

TheF _N method of solving problems in radiative transfer for plane-parallel media with anisotropic scattering is established. The method utilizes properties of the exact solution and leads to final equations that are particularly concise and easy to use.     

A new model for X-ray emission from NGC 4151

We present an analysis of the reported spectral features of NGC 4151 in X-rays. It is shown that the origin of X-rays from the source is inconsistent with a single production mechanism. We suggest a new two-component model in which soft X-rays arise from the black-body emission of a tiny hot nucleus withT2×10⁷ K and the hard X-ray photons are generated in an extended region by inverse Compton scattering of electrons with the infrared photons.     

The evolution of massive close binaries

The results of evolutionary computations for massive binary systems (initial masses of the primary 10M ) with mass ratios between 0.3 and 0.8 are summarized and compared with observations in order to verify how far one can go with the conservative assumption of mass exchange. It is found that conservative mass exchange leads to acceptable first-order models of W-R and massive X-ray binaries. However, the comparison between this theory and observation reveals that for the observed systems (W-R and X-ray binaries) a preference exists for low intial mass ratios; moreover, the X-ray luminosities of the theoretical models are systematically too low, though this may be due to the adopted wind model. In addition, the influences of several parameters (distance between the components, chemical composition, primary mass, mass ratio and atmosphere) are examined. These parameters influence the remnant mass and any further evolution only marginally. Attention is also given to the effect on the system parameters of a supernova explosion of the remnant of the mass-losing component. For a large range of systems a disruption probability smaller than 25% is found.     

Reflectance spectra for sodium and potassium doped ammonia frosts: Implications for Io's surface

This paper reports measurements of the reflection spectra of sodium and potassium doped ammonia frosts as a function of alkali metal concentration which cover the wavelength range 0.35–2.5 μm. The purpose of the measurements was to determine whether or not the reflection spectra for such a solid was compatible with the spectral albedo of Io. The data show that with a sufficiently large alkali metal concentration, the reflection spectra of the doped ammonia frost do not display the characteristic ammonia features at 2.0 and 2.25 μm. The high reflectance of the more concentrated samples and the character of the observed reflection spectrum make it difficult to rule out sodium doped ammonia frost as a surface constituent on Io on the basis of existing data.     

On the dissociation of nitrogen by electron impact and by E.U.V. photo-absorption

The dissociation of N₂ by electron impact and by e.u.v. photo-absorption is studied, and it is shown that the forbidden predissociation of the numerous ¹Π_u and ¹Σ_u⁺ valence and Rydberg states of N₂ in the 11–24eV energy range is the dominant mechanism for N atom production. By measuring the absolute emission cross sections for the e.u.v. singlet bands of N₂ and by using the generalized oscillator strength data of Lassettre (1974), it has been possible to construct a detailed model of the total N₂ dissociation cross section which is in good agreement with the measurements of Winters (1966) and Niehaus (1967) and provides some insights into the maximum possible $\text{N(}{}^2\text{D)}$ yield from dissociative excitation. The total cross section for exciting N₂ e.u.v. radiation in the 800Å–1100Å wavelength range has been measured and found to have a value of 3.4 ×10^?17 cm² at 100 eV under optically thin conditions. Although this result implies that large fluxes of e.u.v. photons should be excited in auroral substorms and in the airglow, they are not observed, and we show that this development is a consequence of radiation entrapment and predissociation. The total cross section for dissociating N₂ by electron impact is given for optically thin and thick media. And some questions concerning the energy budget of a magnetospheric storm which are raised by these results, are discussed.