Showing papers by "Goddard Space Flight Center published in 1972"
TL;DR: The correlation between the azimuthal direction of the interplanetary magnetic field and the most simple polar cap signatures is discussed in this article, where only the spatial distribution of the dawn-dusk polar cap field is considered.
Abstract: The correlations between the azimuthal direction of the interplanetary magnetic field and the most simple polar cap signatures are discussed. Only the spatial distribution of the dawn-dusk polar cap field is considered. For each OGO 6 traverse across the northern or southern polar cap, the simultaneous values of the interplanetary magnetic field in solar-equatorial coordinates were recorded by the Explorer 33 magnetometer. Histograms of these values are presented and are discussed. The high degree of correlation with the longitudinal angle indicates that the relative geometry of the interplanetary magnetic field and magnetospheric magnetic fields must be fundamental to explaining the distribution of polar cap electric fields. The sign of the solar-equatorial component perpendicular to the sun-earth line appears to be a more critical parameter than the sign of the component toward the sun. The Svalgaard-Mansurov correlation and the correspondence between fast convection and parallel magnetospheric and interplanetary magnetic fields are described.
427 citations
TL;DR: In this article, spectral features due to the atmospheric dust storm indicate that large diurnal variations in atmospheric temperature existed up to at least 30 km; winds inferred from the temperature fields show a strong tidal component and significant ageostrophic behavior.
313 citations
TL;DR: In this article, the effect of variation in cloudiness on the climate is considered in terms of a relation between the radiation balance of the earth-atmosphere system and variations in the amount of cloud cover or effective cloud top height.
Abstract: The effect of variation in cloudiness on the climate is considered in terms of 1) a relation between the radiation balance of the earth-atmosphere system and variations in the amount of cloud cover or effective cloud top height, 2) the effect on the surface temperature of variations in cloudiness, and 3) the dynamic coupling or “feedback” effects relating changes in surface temperature to the formation of clouds. The first two points are studied by numerical integration of a simple radiation flux model, and the third point is discussed qualitatively. Global-average radiation balance calculations show that an increase in the amount of low and middle level cloud cover (with cloud top height and cloud albedo fixed) decreases the surface temperature. But, this result for the global-average case does not hold near polar regions, where the albedo of the cloudy areas can he comparable to (or even smaller than) the albedo of the snow-covered cloudless areas, and where, especially in the winter season, th...
274 citations
TL;DR: In this paper, the authors used a fully implicit Lagrangian, hydrodynamic computer code incorporating a nuclear reaction network to follow thermonuclear runaways in the hydrogen-rich envelopes of white dwarfs in order to produce a nova outburst.
Abstract: We have used a fully implicit, Lagrangian, hydrodynamic computer code incorporating a nuclear reaction network to follow thermonuclear runaways in the hydrogen-rich envelopes of white dwarfs in order to produce a nova outburst. Because of the short time-scales and the high nuclear burning rates produced in our models, the nuclear reactions are far out of equilibrium and the beta-plus unstable nuclei become the most abundant nuclei in the envelope except for hydrogen and helium. Our models have ejected 1.00017 solar mass with kinetic energies of 8 times 10 to the 44-th power ergs, a value that agrees quite closely with the observed values for novae.
210 citations
TL;DR: The OGO-6 electric field measurements make it clear that the general pattern of high latitude electric fields in magnetic time-invariant latitude coordinates is not highly variable and that when unusual variations, or field distributions, occur they are relatively isolated in time and spatial extent as mentioned in this paper.
203 citations
TL;DR: In this article, the authors measured the energy spectra of cosmic-ray protons and He nuclei by an ionization spectrometer flown at balloon altitudes, with an energy range extended from 50 to g 1000 GeV.
Abstract: Differential energy spectra of cosmic-ray protons and He nuclei have been measured for the first time by an ionization spectrometer flown at balloon altitudes. The energy range extended from 50 to g 1000 GeV. The observed differential intensities can be represented with power-law spectra with a slope of -2.75 \ifmmode\pm\else\textpm\fi{} 0.03 for protons and of -2.77 \ifmmode\pm\else\textpm\fi{} 0.05 for He nuclei. The proton-to-He ratio is 26 \ifmmode\pm\else\textpm\fi{} 3 at 40 GeV/nucleon and is constant within errors up to 400 GeV/nucleon.
197 citations
177 citations
TL;DR: In this paper, the effects of substorm activity, interplanetary magnetic field latitutde, and dipole tilt angle on high-latitude precipitation of 700 eV electrons were studied.
Abstract: Data from the auroral particles experiment on OGO-4 were used to study effects of substorm activity, interplanetary magnetic field latitutde, and dipole tilt angle on high-latitude precipitation of 700 eV electrons. It was found that: (1) The high-latitude zone of 700 eV electron precipitation in late evening and early morning hours moves equatorward by 5 to 10 deg during substorms. (2) The low-latitude boundary of polar cusp electron precipitation at 9 to 15 hours MLT also moves equatorward by several degrees during substorms and, in the absence of significant substorm activity, after a period of southward interplanetary magnetic field. (3) With times containing substorm activity or a southward interplanetary magnetic field eliminated, the low-latitude boundary of polar cusp electron precipitation is found to move by approximately 4 deg over the total yearly range of tilt angles. At maximum winter and summer conditions the invariant latitude of the boundary is shown to shift by approximately -3 deg and +1 deg respectively from its equinox location.
173 citations
TL;DR: Some eclogitic and ultrabasic inclusions, their separated minerals, host rocks, and related samples have been analyzed by mass-spectrometric isotope dilution for K, Rb, Sr, Ba and rare-earth elements (RE), and by other techniques for selected major elements as discussed by the authors.
170 citations
TL;DR: In this paper, the effects of line shape and band structure on the radiative equilibrium temperature profile in planetary atmospheres have been examined and a method for calculating radiative terms is developed which avoids the usual approximations.
Abstract: Numerical experiments are performed to examine the effects of line shape and band structure on the radiative equilibrium temperature profile in planetary atmospheres. In order to accurately determine these effects, a method for calculating radiative terms is developed which avoids the usual approximations. It differs from the more commonly used methods in that it allows arbitrary dependence of the absorption coefficient on wave number, without requiring tedious line by line integration and without the constraints of band models. The present formulation is restricted to homogeneous atmospheres but the concept can be extended to the more general case. The numerical experiments reveal that the line shape and band structure of the absorbing gases have a large effect on temperatures in the higher layers of the atmosphere (corresponding to the stratosphere and mesosphere). The more nongrey the spectrum (that is, the higher the peaks and the deeper the troughs in the spectrum), the lower the temperature.
152 citations
TL;DR: In this article, a magnetic storm was used as an effective mechanism for removing atomic oxygen at high latitudes in the atmosphere during magnetic storms. But the mechanism was not suitable for high-latitudes.
TL;DR: Satellite observations of energetic particles ejected from the sun generate radio waves as they travel out through the interplanetary medium, including the gross magnetic field configuration over distances of 1 astronomical unit.
Abstract: Energetic particles ejected from the sun generate radio waves as they travel out through the interplanetary medium Satellite observations of this emission at long radio wavelengths provide a means of investigating properties of the interplanetary medium, including the gross magnetic field configuration over distances of 1 astronomical unit Results of such observations are illustrated
TL;DR: In this paper, the Backus-Gilbert theory is applied to the problem of the vertical sounding of the atmosphere by means of remote radiation measurements, and tradeoff curves are presented which quantitatively define the relationship between intrinsic vertical resolution and random error in temperature profile estimates.
Abstract: The Backus-Gilbert theory is applied to the problem of the vertical sounding of the atmosphere by means of remote radiation measurements. An application is made to spectral intervals 2.8/cm wide in the 667/cm band of CO2, and tradeoff curves are presented which quantitatively define the relationship between intrinsic vertical resolution and random error in temperature profile estimates. It is found that for a 1-2K random error with state-of-the-art instrumentation, the intrinsic vertical resolution ranges from approximately 0.5 local scale height (l.s.h.) in the lower troposphere to 2 l.s.h. in the upper stratosphere with approximately 2 l.s.h. resolution in the vicinity of the tropopause. These values are somewhat smaller than the widths of the radiactive transfer kernels at similar levels. Increasing the number of spectral intervals from 7 to 16 is found to produce only a marginal improvement in vertical resolution.
TL;DR: The results indicate the existence of a differential lunar highland crust, probably feldspathic, related to the plagioclase-rich materials previously found in the samples from Apollo 11, Apollo 12, Apollo 14, Apollo 15, and Luna 16.
Abstract: Although only part of the information from the x-ray fluorescence geochemical experiment has been analyzed, it is clear that the experiment was highly successful. Significant compositional differences among and possibly within the maria and highlands have been detected. When viewed in the light of analyzed lunar rocks and soil samples, and the data from other lunar orbital experiments (in particular, the Apollo 15 gamma-ray spectroscopy experiment), the results indicate the existence of a differential lunar highland crust, probably feldspathic. This crust appears to be related to the plagioclase-rich materials previously found in the samples from Apollo 11, Apollo 12, Apollo 14, Apollo 15, and Luna 16.
TL;DR: Large portions of the thermal emission spectra are significantly affected by dust with a silicon oxide content approximately corresponding to that of an intermediate igneous rock, thus implying that Mars has undergone substantial geochemical differentiation.
Abstract: The Mariner 9 infrared spectroscopy experiment has provided goodquality spectra of many areas of Mars, predominantly in the southern hemisphere. Large portions of the thermal emission spectra are significantly affected by dust with a silicon oxide content approximately corresponding to that of an intermediate igneous rock, thus implying that Mars has undergone substantial geochemical differentiation. Derived temperature profiles indicate a warm daytime upper atmosphere with a strong warming over the south polar cap. Atmospheric water vapor is clearly observed over the south polar area and less strongly over other regions.
TL;DR: In this article, a three-dimensional model for the annual and semiannual variations of the thermosphere is presented in which energy and diffusive mass transport associated with the global circulation are considered in a self-consistent form.
Abstract: A three-dimensional model for the annual and semiannual variations of the thermosphere is presented in which energy and diffusive mass transport associated with the global circulation are considered in a self-consistent form It is shown that these processes play a major role in the thermosphere dynamics and account for a number of temperature and compositional phenomena
TL;DR: In this paper, the plasmapause was detected as a global phenomenon both by VLF and ion composition measurements, and the electron and ion density troughs were identified primarily as nightside features.
Abstract: Extensive observations of mid-latitude depletions in electron and total ion density by both direct and indirect techniques, have prompted numerous studies of the possible association between these troughs, observed in the F-region, the topside ionosphere, and the plasmapause. One basic problem arises, in that while the plasmapause was detected as a global phenomenon both by VLF and ion composition measurements, the electron and ion density troughs were identified primarily as nightside features. This problem, as well as the difficulty in explaining various inconsistencies in relating the position of the plasmapause and the ionization trough, is explained by a close examination of the ion composition. In particular, ion composition results from the polar orbiting OGO satellites identify the persistence of a pronounced light ion trough in H(+) and He(+) identified by order of magnitude decreases in the light ion concentrations.
TL;DR: In this article, the main characteristics of free oscillations of the sun are described, and the sources and sinks of energy are estimated, and an estimate of how this energy might be distributed among the more interesting modes.
Abstract: The main characteristics of free oscillations of the sun are described, and the sources and sinks of energy are estimated. Adiabatic oscillations and damping are considered. It is shown how a large solar flare can exert a significant mechanical impulse on the sun by causing a wave of compression to move subsonically into the interior. The solar interior does not easily dissipate low-amplitude acoustical energy, and therefore a relatively large fraction of the energy should remain available to go into the normal modes. An estimate is made of how this energy might be distributed among the more interesting modes.
TL;DR: In this paper, the internal structure of geomagnetic tail neutral sheet deduced from Explorer 34 magnetic data was modeled using models for internal structures of the magnetometer and magnetometer.
Abstract: Models for internal structure of geomagnetic tail neutral sheet deduced from Explorer 34 magnetic data
01 Jan 1972
TL;DR: In this article, a study of several related turbulence approximations with regard to dynamical properties and agreement of numerical predictions with laboratory and computer experiments is presented. But the authors do not discuss the physical and mathematical differences between the model dynamics and actual Navier-Stokes dynamics.
Abstract: Study of several related turbulence approximations with regard to dynamical properties and agreement of numerical predictions with laboratory and computer experiments. The approximations considered include the direct-interaction equations (Kraichnan, 1964), Herring's (1966) self-consistent-field theory, a generalization of Edwards' (1964) theory, the abridged Lagrangian-history, direct-interaction approximation (Kraichnan, 1966), the test-field model (Kraichnan, 1971), and an approximation, not previously described, in which one velocity field passively suffers convection by another. Most of the cited approximations are representable by stochastic model equations for the velocity amplitude. Explicit constructions are given for the stochastic models, in a form that can be approximated on a digital computer. These constructions are used to discuss the physical and mathematical differences between the model dynamics and actual Navier-Stokes dynamics.-
01 Sep 1972
TL;DR: In this paper, the use of two magnetometers for measuring the ambient magnetic field of spacecraft is compared with the single magnetometer variance method, and it is shown that the dual magnetometer concept was developed for missions which are conducted with attitude stabilized spacecraft which have been constructed without an adequate magnetics control program.
Abstract: The use of two magnetometers for measuring the ambient magnetic field of spacecraft is compared with the single magnetometer variance method. It is shown that the dual magnetometer concept was developed for missions which are conducted with attitude stabilized spacecraft which have been constructed without an adequate magnetics control program. Specific methods for applying the dual magnetometer technique are described and an error analysis is conducted to determine the accuracy of the results.
TL;DR: In this paper, a model for solar microwave bursts is considered in which over a broad frequency band the flux density is a slowly varying function of frequency, and it is proposed that such an essentially flat spectrum could result from free-free absorption of gyrosynchrotron emission of nonthermal electrons accelerated in solar flares.
Abstract: : A model for solar microwave bursts is considered in which over a broad frequency band the flux density is a slowly varying function of frequency. It is proposed that such an essentially flat spectrum could result from free-free absorption of gyrosynchrotron emission of nonthermal electrons accelerated in solar flares. The theory of gyrosynchrotron radiation is reviewed, and simplified formulae for the Razin effect, selfabsorption and gyroresonance absorption are given and their range of validity is discussed. Using these results the thermal electron density, temperature, emission measure, magnetic fields and number of nonthermal electrons in the emitting region are evaluated for a flare with a flat microwave spectrum. (Author)
TL;DR: IMP 5 magnetic field measurements at high geomagnetic latitudes to observe broad depressed field region centered on polar or dayside cusp were performed in this paper, where the authors reported that
Abstract: IMP 5 magnetic field measurements at high geomagnetic latitudes to observe broad depressed field region centered on polar or dayside cusp
TL;DR: In this paper, a series of balloon flights in southeastern New Mexico was obtained on microthermal atmospheric turbulence structure from the surface to altitudes of 12 to 15 km and the beginning of the tropopause region.
Abstract: During a series of balloon flights in southeastern New Mexico new data was obtained on microthermal atmospheric turbulence structure from the surface to altitudes of 12 to 15 km and the beginning of the tropopause region. It was possible to compute the temperature structure coefficient and the refractive-index-structure coefficient. The major significance of the data is the thermal evidence for turbulence and the strength of this effect in the upper-altitude regions.
01 Dec 1972
TL;DR: In this paper, the authors describe a model for the accurate analysis of eclipsing binary light curves, which accounts for the important geometric and photometric distortions such as rotational and tidal distortion, gravity brightening, and reflection effect.
Abstract: The accurate analysis of eclipsing binary light curves is fundamental to obtaining information on the physical properties of stars. The model described accounts for the important geometric and photometric distortions such as rotational and tidal distortion, gravity brightening, and reflection effect. This permits a more accurate analysis of interacting eclipsing star systems. The model is designed to be useful to anyone with moderate computing resources. The programs, written in FORTRAN 4 for the IBM 360, consume about 80k bytes of core. The FORTRAN program listings are provided, and the computational aspects are described in some detail.
01 Jan 1972
TL;DR: In this article, two techniques, tracking the motions of Ba(+) clouds and measuring the differences in floating potential between symmetric double probes, were used to demonstrate the basic convective nature of magnetospheric electric fields, mapping global patterns of convection at upper ionosphere levels, and revealing the physics of electric currents in the ionosphere and the importance of magnetosphere-ionosphere feedback in altering the imposed convection.
Abstract: Two techniques, tracking the motions of Ba(+) clouds and measuring the differences in floating potential between symmetric double probes, were successful in: (1) demonstrating the basic convective nature of magnetospheric electric fields, (2) mapping global patterns of convection at upper ionosphere levels, and (3) revealing the physics of electric currents in the ionosphere and the importance of magnetosphere-ionosphere feedback in altering the imposed convection.
TL;DR: Simulation of sensor spatial resolution effects on estimates of cloud cover from satellites is presented in this article, where the authors simulate the effects of spatial resolution on cloud coverage from satellite data.
Abstract: Simulation of sensor spatial resolution effects on estimates of cloud cover from satellites
TL;DR: In this paper, the differential and total ionization cross sections of 11 atoms and one ion by electron impact, and ionization of helium by proton impact were calculated using plane waves to describe the incident and scattered particles and screened hydrogenic and Coulomb functions to describe atomic electrons before and after ejections.
Abstract: Using plane waves to describe the incident and scattered particles, and screened hydrogenic and Coulomb functions to describe the atomic electrons before and after ejections, we have calculated the differential and total ionization cross sections of 11 atoms and one ion by electron impact, and ionization of helium by proton impact. The effective charges of the screened hydrogenic functions are fixed by the Hartree-Fock calculations. Calculations have been carried out for the atomic s, p, and d electrons. For low atomic numbers, we find reasonable agreement with the experimental data. For intermediate atomic numbers, we expect our results to overestimate the actual cross sections, since our choice of a unit charge for the Coulomb function of the ejected electrons will overestimate the atomic dipole potential strength, and in turn the high-energy cross sections. The advantage of the method presented here is that the ionization amplitude is given in analytic form. This may allow further analysis on this amplitude, and facilitates extension of the numerical integration for the cross section to high impact energies.
TL;DR: In this article, a model of the ionospheric plasma is described by means of the momentum and continuity equations for O +, He +, H + and the energy equations for T e and T i.
TL;DR: In this article, the delta B distribution of the Ogo 3 and 5 satellites has been used to deduce the primary source of the large field reductions inside the plasmasphere is a population of low-energy protons with energies of 0.1-1 Mev.
Abstract: The delta B distribution deduced from the Ogo 3 and 5 satellites shows large field depressions in the equatorial region inside the plasmasphere. On the basis of the delta B distribution, it is shown that what is usually considered the quiet-time ring current is an equatorial sheet current that is an extension of the neutral sheet current in the magnetospheric tail. The primary source of the large field reductions inside the plasmasphere is a population of protons with energies of 0.1-1 Mev initially detected by Davis and Williamson (1963) and Davis (1965) on Explorer 12, 14, and 15. Low-energy protons extensively measured on Ogo 3 by Frank (1967, 1971) are primarily responsible for the current near and outside the plasmapause.