摘要:

There has been some recent controversy over the precise nature of the conditions to be imposed at the core‐mantle boundary when the Earth suffers a static deformation. We here define static deformation by requiring the fluid core to be in hydrostatic equilibrium both before and after the deformation, and then show how to determine the fluid response in terms of the gravitational potential and normal stress, without reference to particle displacement. The core‐mantle boundary is modelled by a thin transition layer between the solid and the fluid in which the rigidity drops to zero. A careful examination of the jump conditions across the transition layer leads to the conclusion that the variables y1, y2and y6as defined in the solid are all discontinu

ISSN:0094-8276    

DOI:10.1029/GL002i001p00001

年代:1975

数据来源: WILEY

摘要:

We analyze slowness and azimuth anomalies, as recorded in the French Polynesia Seismic Network. The network can be considered as an array in its whole, or can be split into two subarrays, 350 km apart. In the former case, it is found that, contrary to Canadian VASA results, no anomaly is apparent for rays bottoming under Hawaii. In the latter case, a model of the crust is attempted under Tahiti as well as under the atoll of Rangiroa.

ISSN:0094-8276    

DOI:10.1029/GL002i001p00005

年代:1975

数据来源: WILEY

摘要:

Synthetic spinel (MgAl2O4) has been found to disproportionate into a mixture of its component oxides, periclase and corundum, at a loading pressure of about 180 kbar and between 1000 and 1400°C. The polycrystalline powder sample was compressed in a diamond‐anvil cell and heated by a continuous YAG laser. The exact transition pressure is not known due to transient increases in pressure during the local and rapid heating process. The phase boundary, however, has been calculated to be P(kbar) = (137±8) + 0.009T(°C) on the basis of the available thermochemical data and compression curves for MgAl2O4, MgO, and A

ISSN:0094-8276    

DOI:10.1029/GL002i001p00009

年代:1975

数据来源: WILEY

摘要:

Wind, temperature and humidity profiles obtained in a wind‐water‐wave channel with four variations of the interfacial conditions were analyzed in order to assess the influence that the free surface conditions have on the fluxes under near neutral stability conditions. The dimensionless humidity gradient remained essentially constant at 1.2 for all surface variations except for the case of suppressed waves where its value was 0.86. On the other hand, the dimensionless temperature gradient demonstrates a definite response to changes in surface conditions and ranges from 0.73 for the suppressed wave case to as high as 1.41 for the larger wind speed (11 m/s), wind‐wave cases. Comparing the results from the suppressed surface and wind‐wave cases for U∞= 10 m/s it was observed that the total energy (sensible plus latent heat) transfer remained constant. However, sensible heat flux increased with the suppression of the wind waves whereas latent heat flux

ISSN:0094-8276    

DOI:10.1029/GL002i001p00012

年代:1975

数据来源: WILEY

摘要:

Measurements of wind speed were made between 31 March and 12 April, 1972 with sensitive cup anemometers at five heights in geometric progression from 25 cm to 4 m above the surface of a gently hummocked ice floe at each of two observation masts which were placed 250 m apart at the site of the main camp of the 1972 AIDJEX pilot experiments. The data were averaged for one‐hour periods and have been used to determine the air drag coefficient on the 64 occasions when the vertical profile of wind varied logarithmically with height and to study the horizontal homogeneity of the wind field in the boundary layer. Mean values of the drag coefficient, for winds extrapolated to the 10 m level, were 1.58 × 10−3at one location with a standard deviation for an individual value of 0.19 × 10−3and 1.74 × 10−3± 0.25 × 10−3at the other. The corresponding values of roughness length zowere 0.04

ISSN:0094-8276    

DOI:10.1029/GL002i001p00015

年代:1975

数据来源: WILEY

摘要:

A large 40.475 MHz Doppler radar has been constructed near Sunset, Colorado, 16 km west of Boulder, in order to study winds, the troposphere, stratosphere, and mesosphere. Early results from the troposphere are presented here. It is concluded that: (1) With a sensitive VHF radar it is possible to detect echoes from throughout the upper troposphere almost all the time, under both clear and cloudy conditions; (2) Horizontal winds derived from the Doppler shifts of the echoes are consistent at heights more than 2 km above the local terrain with rawinsonde winds measured over 55 km away; (3) The reflectivity of the scatterers in the troposphere is not strongly aspect sensitive, up to an angle of 30° from the zenith

ISSN:0094-8276    

DOI:10.1029/GL002i001p00019

年代:1975

数据来源: WILEY

摘要:

A comparison is made between two independent measurements and calculated values of j (NO2), the photolysis frequency of NO2. The calculated value was approximately 2% greater than the frequency implied by observations. This discrepancy is small enough to confirm the general accuracy of the computational technique and its associated input parameters.

ISSN:0094-8276    

DOI:10.1029/GL002i001p00022

年代:1975

数据来源: WILEY

摘要:

Vertical distributions of particles (0.1 µm radius) and gases are derived for a simplified model of the stratosphere. A constant source acts at a specific range of heights, and the troposphere is a sink. Gravitational settling is shown to have a large effect on the distribution and residence time of the particles. This effect cannot be ignored in derivation of vertical eddy coefficients from tracer data, and is of the right magnitude to reconcile the results obtained from particulate and gaseous radioactivity

ISSN:0094-8276    

DOI:10.1029/GL002i001p00026

年代:1975

数据来源: WILEY

摘要:

From a stepwise‐heating experiment to neutron‐irradiated samples of whole rock and a plagioclase separate, we have determined an40Ar ‐39Ar age of 4.26 ± 0.02 G.y. for the Apollo 17 troctolite 76535. This rock is believed to have formed as a result of very slow cooling at a depth of 10 ‐ 40 km, and hence furnishes direct evidence that the moon was chemically zoned before 4.26 G.y. The age of the rock is associated with the Serenitatis Basin forming event. The age of formation of the Serenitatis Basin is then deduced at 4.26 ± 0.02 G.y. ago, about 300 million years before the Imbrium event. It appears that the major basin forming era on the near side of the moon lasted longer than 300 million years. The grouping of many lunar rock ages at 3.9 ‐ 4.0 G.y. is most likely due to the fact that the Imbrium ejecta predominates all highland la

ISSN:0094-8276    

DOI:10.1029/GL002i001p00029

年代:1975

数据来源: WILEY

摘要:

Improved instrumentation in the x‐ray photoelectron spectrometer allowed the first direct observation of the change of valence state of iron in the silicate Fayalite under helium‐ion bombardment. From the observed ion dosage necessary to reduce the iron in the topmost atomic layers to the metallic state it is estimated that similar reduction on the lunar surface under solar‐wind proton bombardment would occur between 700 to 1000 years. Within such a time scale, it seems likely that all surface iron in the iron‐containing lunar fines should have been reduced to the metallic state. Implications of these experimental observations in terms of various proposed darkening mechanisms are di

ISSN:0094-8276    

DOI:10.1029/GL002i001p00033

年代:1975

数据来源: WILEY