摘要:

Changes in ozone, temperature, and other minor constituents resulting from eleven‐year variations in the solar flux between 180 and 340 nm are presented. Results were computed using a one‐dimensional time dependent model that allows for all major feedbacks and time delays which may result from changing photolysis rates in the Ox‐ NOx‐ HOx‐ CℓOxsystem.Since the 1950's the chlorine content of the stratosphere has been increasing. The effect of this increase on ozone variability during the last two solar cycles is analyzed. Expected variations in O3and temperature resulting from changes in the uv flux are compared to available m

ISSN:0094-8276    

DOI:10.1029/GL005i010p00817

年代:1978

数据来源: WILEY

摘要:

The observation of an “electron hopping phenomenon” in ilvaite, CaFe22+Fe3+Si208(OH), has been made by previous workers. The effect of temperature on Fe2+→Fe3+electron delocalization in ilvaite is closely investigated in the present study. Mössbauer spectra of a suite of naturally‐occurring ilvaites were recorded over a range of temperatures, 80K to 575K. Delocalization is readily confirmed in the spectra with appearance of species with parameters intermediate to Fe2+and Fe3+. Contrary to prior investigations, five doublets are required to fit the spectra and are assigned to Fe3+(A), Fe2+(A), Fe2+(B), and Fe2+(A)→Fe3+(A) ∥c and ⊥c. Doublets associated with delocalization are resolved at 80K and preclude the use of an order‐disorder transition model. We propose a thermal activation model and draw some implications for geophysi

ISSN:0094-8276    

DOI:10.1029/GL005i010p00821

年代:1978

数据来源: WILEY

摘要:

A 200 year old brain coral, captured in Bermuda in 1976 was slabbed and x‐rayed. Using the annual growth bands sequential, dated samples were taken over the entire growth period of the coral and analyzed for Δ14C, δ13C and δ18O. During the past 80 years atmospheric variations in Δ14C and δ13C due to human effects, such as release of bomb C‐14 and dilution of both C‐14 and C‐13 by fossil fuel burning, are closely tracked by the coral. Prior to 1900 divergences between the coral and tree Δ14C and δ13C can be related to world‐wide changes in plant production and possibly oceanic

ISSN:0094-8276    

DOI:10.1029/GL005i010p00825

年代:1978

数据来源: WILEY

摘要:

The absolute rate constant for the reaction Cl + H2CO → HCl + HCO has been determined by the flash‐photolysis‐resonance fluorescence method to be 7.5 ± 0.9 (2σ) × 10−11cm³ molecule−1sec−1at 298K and to have a negligible temperature dependence. This rate which at stratospheric temperatures is more than 2000 times faster than the rate of Cl + CH4and more than a factor of 2 faster than Cl + HO2, indicates that formaldehyde (H2CO) will compete significantly with methane (CH4) and HO2for the conversion of active chlorine in the stratosphere to the inactive reservoir HCl. Chlorine will thus be a less efficient destroyer of stratospheric ozone than previously believed. One‐dimensional eddy‐diffusion photochemical model calculations indicate that the eventual ozone depletion for a steady‐state CFM release at 1975 rates (750,000 tons/year) will be lowered from 20% to 18.5% by the inclu

ISSN:0094-8276    

DOI:10.1029/GL005i010p00829

年代:1978

数据来源: WILEY

摘要:

A large granite sample containing a saw‐cut filled with crushed granite, modeling a natural fault with gouge, was loaded triaxially at confining pressure of 400 MPa. Changes in pore volume of the simulated gouge layer were measured during application of confining pressure and during axial loading to failure by sudden stick‐slip. Pore volume strain in this configuration, with a thin layer of gouge between rock surfaces, was significantly less with increasing confining pressure than in similar experiments in which the entire sample was of crushed granite. Our sample continued to decrease in volume upon application of axial load up to the point at which sliding on the saw‐cut started. At this point, the decrease in volume slowed down, and the volume increased just before failure. Failure occurred at a stress below that required to cause dilatancy in intact rock, suggesting that gouge might show premonitory changes before earthquakes that would not appear in intact rock surrounding a fault

ISSN:0094-8276    

DOI:10.1029/GL005i010p00832

年代:1978

数据来源: WILEY

摘要:

Nighttime thermospheric winds and temperatures over Fritz Peak Observatory (39.9°N, 105.5°W) have been determined from the Doppler shifts and line profiles of the (OI) 15876‐K (6300 Å) line emission. The peak winds measured during several geomagnetic storms are shown to be linearly related to the time rate of change of the equatorial ring current parameter (d(DSt)/dt). During these geomagnetic storm periods the time variation of the measured meridional winds are also strongly correlated with the time rate of change of DStalthough the observed winds at midlatitudes may lag variations in this parameter by several hours. The energy input derived from d(DSt)/dt is consistent with the high latitude energy input that is necessary in a thermospheric dynamic model to bring the calculated meridional winds into agreement with the observations. These results suggest that d(DSt)/dt is a useful index for determining the magnitude and time history of the high latitude energy input during both quiet and disturbed geomagnetic conditions for use in global thermospheric dynamic mo

ISSN:0094-8276    

DOI:10.1029/GL005i010p00835

年代:1978

数据来源: WILEY

摘要:

The nonlinear evolution of the monochromatic whistler cyclotron resonance is responsible for a wide variety of geomagnetospheric phenomena whose interpretation has not taken into account the concomitant existence of whistler turbulence. Consideration of this whistler noise in the evolution of the coherent cyclotron resonance permits placing upper temporal bounds on the validity of the noiseless description of the interaction, and obtaining estimates for the relative intensity of the coherent mode and turbulent fields required for the onset of a typical nonlinear effect to occur. Particularization to the Siple wave injection experiment suggests that the influence of turbulence might be significant for monochromatic whistlers with weak or medium amplitudes (<100 mγ)

ISSN:0094-8276    

DOI:10.1029/GL005i010p00839

年代:1978

数据来源: WILEY

摘要:

In this paper we apply Boltzmann‐Fokker‐Planck (BFP) theory to analyze the (isotropic) photoelectron flux in the Earth's ionosphere at energies in the vicinity of photoionization peaks where the electron impact cross sections are slowly varying functions of energy. We give a Green's function solution for the photoelectron flux which shows that the energy derivative terms in the BFP method dominate the solution in spectral regions of high slope. Analytical results for the photoelectron flux and the forward and backward half widths in the vicinity of isolated photoionization peaks are given which explain the observed asymmetry and shift of the photoionization peaks with increasing altitude. At low altitudes these results indicate that the theoretical width of an isolated photoionization peak is less than the experimental resolution of recent AE‐E data. A comparison between the theoretical photoelectron flux averaged using the experimental resolution and the experimental photoelectron flux from 15 to 35 eV at 182 km shows reasonable relative agre

ISSN:0094-8276    

DOI:10.1029/GL005i010p00843

年代:1978

数据来源: WILEY

摘要:

A drift‐tube mass‐spectrometer apparatus has been used to determine the rate coefficients for the loss of O++ions by charge transfer on collisions with N2and O2molecules. At 300 K the respective coefficients are (1.3 ± 0.3) × 10−9and (1.5 ± 0.3) × 10−9cm³/sec. Even at F‐region temperatures these reactions should be fast, since the rate coefficients for reactions of this type vary only slightly with increase in temperature. However, in the recent model calculations of Breig et al, the AE measurements of the O++altitude profiles are only reproduced if the O+++ N2rate coefficient is assumed to be much smaller than 10−10cm³/sec. Thus we conclude that important sources of O++ions have been omitt

ISSN:0094-8276    

DOI:10.1029/GL005i010p00847

年代:1978

数据来源: WILEY

摘要:

A recently reported standing Alfvén wave at ATS 6 is reinterpreted using axisymmetric toroidal‐mode solutions which involve realistic ionospheric height‐integrated conductivities. Details of possible wave‐forms are deduced, and it is suggested that the wave may be interpreted as either a modified form of the classical half‐wave resonance, or as an example of the recently predicted quarter‐wave

ISSN:0094-8276    

DOI:10.1029/GL005i010p00849

年代:1978

数据来源: WILEY