摘要:

Modern studies of solar‐terrestrial relations require a new type of solar activity indices suitable for numerical computations. Since in this context solar extreme ultraviolet radiation is the most important variable influence, EUV indices are proposed representing the EUV energy flux from the whole solar disc at Earth' distance. Examples derived from AEROS measurements are presente

ISSN:0094-8276    

DOI:10.1029/GL003i010p00573

年代:1976

数据来源: WILEY

摘要:

Reduction of data from the three Mariner 10 encounters to this date have allowed identification of helium and hydrogen as atmospheric constituents. Subsolar point densities are estimated at 4500 cm−3for He and 8 cm−3for the thermal component of H. A non‐thermal component in H with a scale height of ∼ 70 km has been observed near the limb off the subsolar point, providing a total apparent number density of 90 cm−3. Upper limits on other atmospheric constituents have been reduced an order of magnitude. A very tentative identification of O has been obtained but the uncertainty is large and we require further data reduction for con

ISSN:0094-8276    

DOI:10.1029/GL003i010p00577

年代:1976

数据来源: WILEY

摘要:

Analysis of Mariner 10 stereoscopic images of the surface of Mercury suggest that ancient, intercrater plains consist in part of visually indistinct but topographically defined circular depressions inferred to be highly degraded craters and basins. Embayment of some craters within the heavily cratered terrain and transection of basins and craters by intercrater plains suggest that formation of at least some intercrater plains postdates the later portions of the bombardment of Mercury by large objects. On the other hand, superposition of crater ejecta onto portions of intercrater plains in other areas indicates that some large craters formed into a pre‐existing, intercrater plains unit. A single episode of obliteration (to form intercrater plains) or bombardment (to produce the large craters) cannot be reconciled with available observations. A more complex history of contemporaneous crater and plains formation is suggeste

ISSN:0094-8276    

DOI:10.1029/GL003i010p00581

年代:1976

数据来源: WILEY

摘要:

A model of the zodiacal cloud is used to evaluate the effects of rotational bursting on interplanetary dust particles caused by the interaction of solar radiation pressure with the irregular surface geometry of the particles. The effectiveness of this mechanism is evaluated using several values for the effective moment arm and tensile strength of the particles. Due to repeated bursting, it is shown that particles spiraling in from the asteroid belt by the Poynting‐Robertson effect do not penetrate inside 1.2 A.U. Spin rate stabilization under the effect of magnetic damping is found to depend critically on the initial heliocentric distance of the particle and on its radiu

ISSN:0094-8276    

DOI:10.1029/GL003i010p00585

年代:1976

数据来源: WILEY

摘要:

A detailed examination of Mariner 5 magnetic field data reveals evidence for a boundary layer beginning in the dayside ionosphere, and a magnetotail much like the terrestrial magnetotail in accord with Venera measurements.

ISSN:0094-8276    

DOI:10.1029/GL003i010p00589

年代:1976

数据来源: WILEY

摘要:

Examination of slightly over two years of ATS‐1 magnetic field data show that the magnetopause at local noon is within synchronous orbit (6.6 earth radii geocentric) 0.3% of the tim

ISSN:0094-8276    

DOI:10.1029/GL003i010p00593

年代:1976

数据来源: WILEY

摘要:

Observations of structured Pc‐1 pulsations at Siple Station, Antarctica allow comparison of the propagation paths of these signals with previously reported whistler observations. The whistler data have provided a detailed history of the plasmapause location during a six day interval of magnetic disturbance and recovery. Determination of the equatorial distances to the propagation paths of the Pc‐1 signals by dispersion analysis indicates that the hydromagnetic whistlers propagate 1 to 4 R e above the plasmapause. We find, however, that structured Pc‐1 signals are observed only when the plasmapause is near or above the Siple field lines. This suggests that the Pc‐1 signals are propagating in or below the plasmapause and that some of the assumptions of the dispersion analysis may be i

ISSN:0094-8276    

DOI:10.1029/GL003i010p00596

年代:1976

数据来源: WILEY

摘要:

Several thousand earthquakes were recorded by portable seismic stations operated in Guatemala within the first week following the destructive earthquake of February 4, 1976. The seismically active zone followed the Motagua fault through eastern and central Guatemala, and then branched sharply southward about 35 km west of Guatemala City. These data support the conclusion from field evidence that the main earthquake was caused by movement within the Motagua fault zone. A total rupture length of at least 250 km, defining a segment of the active boundary between the North American and Caribbean plates, is inferred. The southward trending zone of aftershock activity may be a newly defined section of the boundary, or a secondary fault.

ISSN:0094-8276    

DOI:10.1029/GL003i010p00599

年代:1976

数据来源: WILEY

摘要:

Measured photoabsorption cross sections for fluorocarbons (FC) 11, 12, 21, and 22 are presented for the wavelength region from 1740Å to about 2200Å. Solar radiation in this region dissociates these molecules in the stratosphere releasing atomic chlorine which participates in catalytic reactions that destroy ozone. Photolysis by solar UV is the only known loss mechanism for FC11 and FC12. However, FC21, and FC22 also react with OH in the troposphere reducing the amount of ground level releases which reach the stratosphere. Calculations comparing the steady state stratospheric ClX due to equal release rates of fluorocarbons 11, 12, 21, and 22 are presented using a range of OH profiles and eddy diffusion coefficients. These calculations indicate approximately a factor of 20 to 450 less ClX in the stratosphere for FC21 and a factor of 40 to 130 for FC22, compared to an equal release rate of FC11 and FC1

ISSN:0094-8276    

DOI:10.1029/GL003i010p00603

年代:1976

数据来源: WILEY

摘要:

The density of molecular hydrogen in the earth's atmosphere has been measured between 95 km and 108 km. The technique involved use of the high resolution ultraviolet spectrometer of the Orbiting Astronomical ObservatoryCopernicusto observe radiation from the γ² Velorum near the R(0) line of the (0,0) Lyman absorption band at 1108Å as the star was occulted by the earth's atmosphere. The result shows H 2 densities varying from 1.05 −0.14+0.15× 108cm−3at 95 km to 1.1 −0.08+0.05× 107cm−3at 108 km. These densities agree quite well with recent theoretical predictions. The measured O 2 density profile generally agrees with the models except for a wave‐like structure between 104

ISSN:0094-8276    

DOI:10.1029/GL003i010p00607

年代:1976

数据来源: WILEY