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The atomic-oxygen laser oscillates at four closely spaced frequencies on the gain profile of the 8446-A fine-structure transitions. A set of experiments is reported which studies the competition among these four lines by suppressing one of them. The results are explained on the basis of the interaction of laser lines oscillating on Doppler-broadened transitions sharing a common lower level.
Examination of the relations between the solar-wind and Comet Bennett during the period from Mar. 23 to Apr. 5, 1970. A large kink was observed in the ion tail of the comet on April 4, but no solar-wind stream was observed in the ecliptic plane which could have caused the kink. Thus, either there was no correlation between the solar wind at the earth and that at Comet Bennett (which was 40 deg above the ecliptic) or the kink was caused by something other than a high-speed stream. The fine structure visible in photographs of the kink favors the second of these alternatives. It is shown that a shock probably passed through Comet Bennett on March 31, but no effect was seen in photographs of the comet. A stream preceded by another shock and a large abrupt change in momentum flux might have intercepted the comet between March 24 and March 28, but again no effect was seen in photographs of the Comet.
The Lorentz half-width alpha (L), of the fine-structure components of the methane 3nu/sub 3/ R-branch in the Jovian spectrum has been measured from photoelectric observations of the singlet R(1). Curves of growth for the 3nu/sub 3/ R-branch manifolds have been calculated, using the measured value of alpha (L) and assuming a reflecting-layer atmosphere. The Walker-Hayes (1967) equivalent widths have been reanalyzed for rotational temperature and methane abundance. The half-width derived here is significantly different from a similar measurement made by Farmer (1969). The source of the discrepancy remains obscure.
The distribution of reciprocal semi-major axes in photographic meteor orbits is studied. A detailed classification of the orbits is made according to quality. The distribution of 1/a in precise orbits is multimodal with two broad maxima approximately centered on 0.05 and 0.40 (AU)/1. Minima in the distribution appear near 0.20 and 0.66 (AU)/1 corresponding to Jupiter's and Mars' position in the 1/a diagram. Considerable fine structure appears in the 1/a distribution. Resonance gaps corresponding to commensurabilities with Jupiter are detected. The gaps are similar to the well studied Kirkwood gaps in the asteroid belt.
A steady state isobaric cloud model is developed. The pressure, thermal, electrical, and chemical balance equations are solved simultaneously with a simple one dimensional approximation to the equation of radiative transfer appropriate to diffuse clouds. Cooling is mainly by CII fine structure transitions, and a variety of heating mechanisms are considered. Particular attention is given to the abundance variation of H2. Inhomogeneous density distributions are obtained because of the attenuation of the interstellar UV field and the conversion from atomic to molecular hyrodgen. The effects of changing the model parameters are described and the applicability of the model to OAO-3 observations is discussed. Good qualitative agreement with the fractional H2 abundance determinations has been obtained. The observed kinetic temperatures near 80 K can also be achieved by grain photoelectron heating. The problem of the electron density is solved taking special account of the various hydrogen ions as well as heavier ones.
The work consists of two parts. The first deals with the fine structure of radio pulses. Based on kinetic theory, processes occurring in the plasma shell of a pulsar when external electromagnetic radiation is present are investigated. It is shown that electromagnetic waves cause electrons to drift relative to ions, and initiate longitudinal oscillations. A dispersion equation describing the longitudinal oscillations in magnetized plasma is derived. Conditions for excitation of oscillations are found. Correlation functions of electron density are calculated, along with the coefficients of electromagnetic wave scattering. It is shown that variations in the amplitude of pulsar pulses are associated with scintillations caused by fluctuations in the plasma electron density. The second part of the study presents a mechanism for the radio emission of pulsars. The model of a rotating and a pulsating star, a neutron star with dipolar or more complex magnetic field, is examined.
A computer code has been developed to study quantitatively the drift motion of magnetospheric particles in a time-dependent electric field. These calculations were applied to the case of proton and electron injections from the plasma sheet during substorms; the model predictions were checked against observations on board the geosynchronous satellite ATS 5 by DeForest and McIlwain (1971). It was found that it is possible to simulate the observed proton spectrograms with an adequate choice of a time-dependent electric field model. The resulting kinematics is physically quite simple and in its gross features does not depend too strongly on the particular fine structure of the model.
The rotational temperature of the 2 nu 3 methane absorptions in the solar/telluric spectrum and the methane abundance in the earth's atmosphere have been measured and are found to be 243.4 plus or minus 5.3 K and 1.137 plus or minus 0.117 cm-atm (STP) in a vertical column, respectively. The data were reduced using the results of laboratory measurements with proper allowance for the fine-structure of the methane absorption manifold and the effects of vibration-rotation interaction (which causes an enhancement of the R-branch of this band).
The beam-foil light source is shown to be very useful in spectroscopic work. Not only the lifetimes of highly excited, multiply charged atoms can be measured in a straightforward way, but also the fine-structure and hyperfine-structure separations and the Lande factors can be obtained due to the fact that the coherent excitations are created in the impulsive beam-foil collision. The theories suggested to explain the origin of coherence are presently incomplete.
The positional analysis of solar bursts at meter and decameter wavelengths observed during the period from July 31 to Aug. 7, 1972 is presented. Most of the activity during this period was associated with the active regions McMath 11976 and 11970. Except near the central meridian passage of region 11976, two regions of continuum emission were observed - one a relatively smooth continuum and the other a continuum superimposed with many type III emissions and other fine structure. It seems possible to interpret these continua in terms of plasma waves originating from two sources located at different heights or with different electron density gradients. The angular size of type III sources seems to increase with decreasing frequency. This implies that the open field lines along which the type III electrons travel have larger angular extent at greater heights.
The three-element interferometer of the National Radio Astronomy observatory and the two-element interferometer of the Hat Creek Observatory have been used to observe the fine structure of the sun at 11.1-, 3.7-, and 1.3-cm wavelengths. Solar active regions have been synthesized at 11.1- and 3.7-cm wavelengths with angular resolutions of 9 and 3 arc sec, respectively. Structural components on the scale of a few seconds of arc have also been detected in the quiet-sun and flare regions.
Ion and electron temperatures, and ion drift were measured in a superconducting magnetic mirror apparatus by observing the Doppler-broadened charge-exchange component of the 667.8 and 587.6 nanometer He lines in He plasma, and the H sub alpha and H sub beta lines in H2 plasma. The second moment of the line profiles was used as the parameter for determining ion temperature. Corrections for magnetic splitting, fine structure, monochromator slit function, and variation in charge-exchange cross section with energy are included. Electron temperatures were measured by the line ratio method for the corona model, and correlations of ion and electron temperatures with plasma parameters are presented.
The detection of a predicted transition, the fine structure line of O3 at 88.16 microns in the H 2 region M17, was reported. Line intensity was measured at 2.2 sub + 7 sub -0.7 times 10 to the 15th power.
A local steady-state isobaric model of the interstellar clouds is developed and applied to the OAO-3 observations. The model allows for cooling by C II fine-structure transitions and for inhomogeneities resulting from attenuations in the external radiations which heat the cloud constituents. Factors affecting the thermal properties of the clouds are emphasized; these include H and H2 balance, interstellar grain heating, electron density, and calcium equilibrium. The thermodynamic consequences of the attenuation of the ultraviolet interstellar radiation field are studied. The effect of varying the most important parameters and their allowed ranges is considered. Results indicate that the model is capable of reproducing the H2 fractional abundances and kinetic temperatures observed by OAO-3.
Laboratory measurements of widths and shifts of the Ca II H and K lines have been made under conditions simulating those in the atmospheres of metallic-line white dwarfs, namely, densities of 10 to the 21st power helium atoms per cu cm and temperatures of 4500 to 6000 K. There are significant differences in the shifts and damping constants of the two fine-structure components. The impact theory is evidently applicable to the Ca II/He system under these conditions, and the observed damping constants are fortuitously close to the predictions of conventional Lindholm-Foley/van der Waals theory. The widths and shifts have also been analyzed in terms of Lennard-Jones potential theory.
Thermal instability in the radiative-cooling region behind a shock will cause upstream density fluctuations to collapse into thin sheets aligned parallel to the shock front. A linearized calculation demonstrates the development of this instability. Thermal conduction suppresses the development of small-scale perturbations. Estimates of the scale sizes for the fully developed condensations agree roughly with the scale sizes of fine structure observed in supernova shells such as the Cygnus Loop.
Aperture synthesis observations at 2.695 GHz and 8.085 GHz of the H II regions NRAO 591, NGC 6857, NGC 7538, M8, W3 and W49A made with the NRAO interferometer are presented. A set of Gaussian functions is derived to describe the radiation distribution of each H II region at each frequency. Fine structure is found in all regions. With the exception of the extended source in W49A, all previously known sources with high excitation parameters are resolved into smaller sources. The electron densities of individual sources range from 100 per cu cm up to 100,000 per cu cm. In NGC 6857, NGC 7538 and W49A, continuum sources smaller than 4 arc sec and with electron densities exceeding 10,000 per cu cm are found close to the known class II OH emission sources. In M8, we find a ring which seems to be split at the position of the O-star Herschel 36.
Extensive high-resolution scans with the Copernicus UV spectrometer are combined with available ground-based data on interstellar lines to obtain temperatures, densities, and abundances in H I clouds and H II regions in the direction of zeta Oph. Column densities are obtained for 21 elements in various ionization stages, and upper limits are reported for 5 elements and 11 molecules. Analysis of radial velocities and growth curves indicates that H2, HD, and most neutral atoms are concentrated in one cloud with a heliocentric velocity of -14.4 km/s and that H II regions exist in addition to the Stroemgren sphere. The electron and proton densities are calculated for the -14.4 km/s cloud, and the temperatures required for the populations of the fine-structure levels in the C I ground state and the excited rotational levels of H2 are computed and indicate that the dense cloud must have some associated hotter regions. Relative to hydrogen, most of the elements in the H I clouds are found to be depleted by factors of 3 to 4000 as compared with solar system abundances, and several elements appear to be depleted in the H II regions as well.