摘要:

A set of forces on the lithospheric plates, including a driving basal shear stress, is deduced and found to be plausibly consistent with the possibility that large‐scale, whole‐mantle convection cells contribute significantly to driving the plates. Fractional and driving plate boundary forces are estimated, and a basal shear stress (BS) is assumed to complete the force balance on each plate. Boundary frictional stresses are assumed to be large (of the order of kilobars), as suggested byHanks[1977]. All BS stresses of significant magnitude are roughly aligned with plate motions. The BS is the only available driving force for the South American and Eurasian plates, and is probably significant in driving most other plates. More generally, the results demonstrate that force models are possible which differ substantially from previous mod

ISSN:0094-8276    

DOI:10.1029/GL005i003p00161

年代:1978

数据来源: WILEY

摘要:

Using data from a topographic and magnetic survey, the magnetization vector of Suiko seamount near the middle of the Emperor seamount chain (44.5°N, 170°E) was calculated. An inclination of −31° ± 9° and a declination of 213° ± 9° was found, although the goodness ratio is poor (R = 1.1). The paleolatitude thus found (17° ± 5°) is significantly different from its present latitude, supporting the theory that the Emperor‐Hawaii chain has been formed by the Hawaiian hot spot. Magnetization of the seamount is reversed, agreeing with the recen

ISSN:0094-8276    

DOI:10.1029/GL005i003p00165

年代:1978

数据来源: WILEY

摘要:

The negative trend between87Sr/86Sr and206Pb/204Pb ratios shown by most oceanic island basalts and the Rb‐Sr and Pb mantle isochrons are ascribed to the end of sulfide segregation, about 2 b.y. ago, in the deep mantle, because this process produces an opposite evolution of µ (238U/204Pb) and Rb/Sr ratios of the residual rocks. These sulfides probably contributed to the core growth. Other isotopic arguments lead to the conclusion of an early and quick core formation; it is, however, proposed here that the core growth continued, but at much slower rate, for ca. 3 b.y. after the initial separati

ISSN:0094-8276    

DOI:10.1029/GL005i003p00169

年代:1978

数据来源: WILEY

摘要:

We have measured dissolved nitrous oxide (N2O) concentrations in Michigan surface waters by equilibration of the water samples with ambient air followed by gas chromatographic analysis of the air. Two rivers and one lake show significant N2O supersaturations (factors of five or more) directly traceable to sewage treatment plant effluents. Municipal tap water samples from 19 U.S. cities also show supersaturations. Our data indicate that chlorination of river water and of wastes might be a key step in N2O production. To measure N2O fluxes from water to air we employ a gas collection device; two initial flux measurements from supersaturated waters are reported.

ISSN:0094-8276    

DOI:10.1029/GL005i003p00173

年代:1978

数据来源: WILEY

摘要:

Measurements of formaldehyde in rain water and on the atmospheric aerosol were performed at several sampling sites in Western Europe. The results are summarized in Table 1. From the data it is concluded that aerosol contributes little to the formaldehyde observed in rain water, and that formaldehyde entering rain water is fairly uniformly distributed along the 50 degree latitude, at least in Western Europe and the Atlantic ocean.

ISSN:0094-8276    

DOI:10.1029/GL005i003p00177

年代:1978

数据来源: WILEY

摘要:

The response of the troposphere at 500 mb level to solar magnetic sector crossings (SMSC) has been investigated in terms of two dynamical atmospheric indices, kinetic energy density and square of the vorticity of the main motion. Daily values of these indices at high and middle latitudes in the Northern Hemisphere for quiet and active solar conditions have been computed using the geostrophic wind approximation. No relationships were found between SMSC and these particular atmospheric indices irrespective of solar activity, latitude, season and interplanetary magnetic field (IMF) polarity. The present investigations lead to conclude that if any effect associated with SMSC is accepted, it should be associated only with the vorticity area index for low pressure trough areas in winter.

ISSN:0094-8276    

DOI:10.1029/GL005i003p00180

年代:1978

数据来源: WILEY

摘要:

A method based on energy balance is used to obtain the thresholds of parametric instabilities of the ‘purely growing’ and ‘arithmetic mean’ varieties which can exist in a plasma irradiated by two or more electromagnetic pump waves. These instabilities produce growing standing electron plasma waves at frequencies satisfying either ω = ωi, where ωiis the frequency of the ithpump wave, or ω = (ωi+ωj)/2, where i and j correspond to two different pump waves. Additionally growing ion standing waves of zero frequency or of frequency (ωi−ωj)/2 are produced. These coherent instabilities are found to be coupled in a sense with the usual ‘decay’ instability and, in the case of three or more pump waves, with each other. The results of this investigation are applied to a recent ionospheric heating experiment described

ISSN:0094-8276    

DOI:10.1029/GL005i003p00183

年代:1978

数据来源: WILEY

摘要:

The response of the ionospheric plasma to multiple pumps is seen in the enhancements of the incoherent scatter plasma line. Two strong HF pumps are transmitted, along with weaker sidebands. The two main pumps have a frequency separation ranging from 0 to 7 kHz. At zero frequency separation the standard decay and purely growing mode instabilities are observed. When two pumps are present, the normal decay instability usually disappears, and is replaced by strong oscillations at the pump frequencies plus features half way between pairs of pumps. These "arithmetic mean" peaks appear in most of the cases observed. The weak transmitted sidebands seem to influence greatly the observed spectra; the theory is treated in a companion paper.

ISSN:0094-8276    

DOI:10.1029/GL005i003p00187

年代:1978

数据来源: WILEY

摘要:

The exact quantum yield of the O (¹D) formation from the ozone photolysis in the UV range 295‐320 nm is important for aeronomic calculations, since O (¹D) is the primary source for OH radicals in the troposphere. Recent O (¹D) quantum yield determinations at 230, 268, 298 and 320 K are summarized and an analytical expression is derived which relates the quantum yield of O (¹D) formation as a function of wavelength and temper

ISSN:0094-8276    

DOI:10.1029/GL005i003p00191

年代:1978

数据来源: WILEY

摘要:

Sulfur concentrations in fine aerosol particles, aerodynamic diameter<1µm, from nonurban coastal and inland locations in South America are generally lower than from locations in North America and the Western North Atlantic. In interior Brazil, sulfur is found exclusively in1µm particles, does not comprise a distinct fine particle mode and may be accounted for by contributions from sea spray and an admixture of air from the interior. In the polar westerlies a similar particle size distribution of sulfur was found. If an upper limit is to be estimated for the concentration of a fine particle mode of sulfur in the “natural” atmosphere, it is less than indicated merely by total sulfur in the<1µm diamete

ISSN:0094-8276    

DOI:10.1029/GL005i003p00195

年代:1978

数据来源: WILEY