摘要:

Chemical, petrographic, isotopic and field studies of igneous‐textured rocks within the Manicouagan structure indicate that they are the product of impact melting. Features of the melt sheet include a high degree of textural variation combined with chemical homogeneity. The textures record a complex thermal history and are due primarily to the interaction of clasts with melt. An inverse correlation between clast abundance and matrix grain size allows the melt sheet to be divided into three vertically gradational units of variable thickness. Chemical homogeneity indicates that the impact melting process has the first order effect of homogenizing heterogeneous target material. The process, however, is not totally effective, because significant (although small) deviations from a calculated average composition exist, particularly in the basal clast‐laden unit. These differences depend on clast composition and abundance. The results presented here are consistent with proposed models for the generation of terrestrial and lunar impact me

ISSN:0094-8276    

DOI:10.1029/GL003i002p00049

年代:1976

数据来源: WILEY

摘要:

The anisotropy of solar flare protons (>3 MeV) evaluated at the time of maximum for each of 24 events measured by the University of Chicago experiments on Pioneers 10 and 11 is observed to decrease gradually between 1 and 4.7 a.u. Since diffusive streaming is related directly to the effective diffusion coefficient parallel to the interplanetary spiral magnetic field (K∥), these observations provide a measure of the radial dependence of interplanetary diffusion parameters. An analysis of these results suggests that K∥ increases gradually with r consistent with a radial dependence given by K∥ (r) = (8±3) × 1021cm²/sec r0.9±.4(r

ISSN:0094-8276    

DOI:10.1029/GL003i002p00053

年代:1976

数据来源: WILEY

摘要:

We propose a high frequency electromagnetic instability of non resonant type, driven by cross current as a source for the onset of substorm expansion phase and the field line reconnection beyond 15RE. By including a normal component of the tail field, BZ, we find that the instability can be quenched provided BZexceeds certain threshold value ‐ 1.8 × 106√Te/λ gauss (0.06 γ, for typical values in the neutral

ISSN:0094-8276    

DOI:10.1029/GL003i002p00057

年代:1976

数据来源: WILEY

摘要:

A filamentation instability of large amplitude whistler waves is observed in a laboratory experiment. The radiation pressure of the wave creates a field‐aligned density trough (δne/ne≃ 40%) in which the wave is ducted. It is predicted that similar nonlinear effects may arise in the ionosphere in connection with the planned high power whistler wave experiments of the AMPS mis

ISSN:0094-8276    

DOI:10.1029/GL003i002p00061

年代:1976

数据来源: WILEY

摘要:

Observations of proton flux in the subsonic flow region of the magnetosheath show double peaks as a function of angle in the equatorial plane of the spacecraft. The peaks are separated by a wide angle, usually more than 90°. Suggestions of double flux peaks are present in 95 percent of the data. They are interpreted as the effect of a persistent pressure anisotropy. The clearest cases were analyzed to determine the orientation of the flux peaks relative to the magnetic field and direction of model hydrodynamic flow. They are shown to be consistent with a greater pressure perpendicular to the field. Possible sources of pressure anisotropy in the magnetosheath are discussed

ISSN:0094-8276    

DOI:10.1029/GL003i002p00065

年代:1976

数据来源: WILEY

摘要:

On Dec. 6, 1974, a Black Brant VB rocket was launched from Cape Parry, N.W.T. into the dayside magnetospheric cleft. The prime launch criterion was the detection of 6300 Å emission by two ground based scanning photometers, but support was provided by two ionosondes. The payload passed through a narrow region of several ergs cm−2sr−1sec−1of soft electron precipitation, a broader region of enhanced electron densities, and a similarly broad region of 0I5577 and 6300 Å emission. At apogee of 236 km the payload had not penetrated into the 5200 Å emission, which had a very sharp equatorward boundary, and extended far into the polar cap, presumably as a result of anti‐sunward

ISSN:0094-8276    

DOI:10.1029/GL003i002p00069

年代:1976

数据来源: WILEY

摘要:

Photodissociation of CSO (and possibly CS2) may provide an interesting stratospheric source of SO2and further conversion of this SO2to H2SO4may contribute significantly to the non‐volcanic background sulfate layer in the stratosphere. Assuming a tropospheric background volume mixing ratio of 2‐3 × 10−10, as indicated by some tropospheric measurements, the input of SO2in the stratosphere coming from the decay of CSO is estimated to be 6 × 106‐ 107molecules cm−2s−1. Little is known about the sources and sinks of CSO. It is, therefore, clear that, as a matter of caution, a possible growth of industrial releases of CSO (and CS2) into the atmosphere, e.g., from coal combustion, should be watched carefully with regard to their influence on the stratospheric aerosol layer and the earth's radi

ISSN:0094-8276    

DOI:10.1029/GL003i002p00073

年代:1976

数据来源: WILEY

摘要:

Ion mass spectrometer data collected onboard the Atmosphere Explorer‐C satellite during the period December 1974‐January 1975 have been used to infer, via the ion chemistry, the molecular oxygen concentration near 250km. To filter out temperature induced variations the O2densities and in situ neutral composition measurements of atomic oxygen were extrapolated down to 120km. At this level the latitudinal and diurnal variations of O are found to be consistent with the ones inferred from OGO‐6 during high levels of solar activity. The results also show that at mid to high northern (winter) latitudes the O2concentration is about a factor of two higher than at low southern (summer) latitudes, thus revealing an apparent reversal of the winter to summer increase in O2deduced from optical and incoherent scatter measurements during higher levels of solar activity. Considering that the winter oxygen bulge in the lower thermosphere apparently prevails throughout the solar cycle the latitudinal (annual) variations in O2can play a decisive role in explaining the reversal of the winter anomaly during minimum solar activity. The diurnal variations in O2reveal a pronounced minimum at 18 LT thus suggesting that photo dissociation of O2is impo

ISSN:0094-8276    

DOI:10.1029/GL003i002p00077

年代:1976

数据来源: WILEY

摘要:

HCl has been observed in the stratosphere from balloon borne spectroscopic measurements of a portion of the fundamental band in the 3 microns wavelength region. The observation of absorption lines using the sun as a source at solar zenith angles larger than 90° indicates an HCl volume mixing ratio equal to (3.8 ± 1.5) × 10−10at 20 km increasing with altitude at least up to 30 km where the value is (1.4 ± 0.6) × 10−9. The total zenith amount above 21 km is found to be (10± 3.5) × 10−14cm−2in agreement with previous observations performed up to this altitude. A maximum number density equal to (7.2 ± 3) × 108cm−3is observed at

ISSN:0094-8276    

DOI:10.1029/GL003i002p00081

年代:1976

数据来源: WILEY

摘要:

Three dimensional velocity models for the earth's mantle were obtained satisfying P, S and some PcP and ScS travel time anomalies from deep focus earthquakes. A method of successive approximation was used to compute the uniform relative velocity perturbation over three dimensional blocks of size 10°×10° in longitude and latitude, and 500 km in thickness. Features of these velocity perturbations indicated that lateral heterogeneity is the most pronounced in the upper mantle and near the core‐mantle boundary. The upper mantle anomalies are correlated with surface tectonic features, but these are not correlated with deep mantle anoma

ISSN:0094-8276    

DOI:10.1029/GL003i002p00084

年代:1976

数据来源: WILEY