Radius of convergence of Lie series for some elliptic elements     

C. J. Cohen  R. H. Lyddane 《Celestial Mechanics and Dynamical Astronomy》1981,25(3):221-234

For equatorial orbits about an oblate body, we show that the Lie series for the elliptic elementse,f,l and diverge when the oblateness exceeds a critical multiple of the transformed eccentricity constant. The use of similar truncated series expansions for such elliptic elements by Brouwer accounts for the first-order errors at low eccentricity in his derived coordinates for an artificial satellite.  相似文献   

The inter-relationship of hard X-ray and EUV bursts during solar flares     

A. Gordon Emslie  John C. Brown  Richard F. Donnelly 《Solar physics》1978,57(1):175-190

A comparison is made between the flux-versus-time profile in the EUV band and the thick target electron flux profile as inferred from hard X-rays for a number of moderately large solar flares. This complements Kane and Donnelly's (1971) study of small flares. The hard X-ray data are from ESRO TD-1A and the EUV inferred from SFD observations.Use of a ₂ minimising method shows that the best overall fit between the profile fine structures obtains for synchronism to 5 s which is within the timing accuracy. This suggests that neither conduction nor convection is fast enough as the primary mechanism of energy transport into the EUV flare and rather favours heating by the electrons themselves or by some MHD wave process much faster than acoustic waves.The electron power deposited, for a thick target model, is however far greater than the EUV luminosity for any reasonable assumptions about the area and depth over which EUV is emitted. This means that either most of the power deposited is conducted away to the optical flare or that only a fraction 1–10% of the X-ray emitting electrons are injected downwards. Recent work on H flare heating strongly favours the latter alternative - i.e. that electrons are mostly confined in the corona.  相似文献   

Editorial     

A. G. W. Cameron  Z. Kopal  C. P. Sonett 《Earth, Moon, and Planets》1978,18(1):3-3

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TheF N method for solving radiative-transfer problems in plane geometry     

C. E. Siewert 《Astrophysics and Space Science》1978,58(1):131-137

TheF _N method of solving problems in radiative transfer for plane-parallel media with anisotropic scattering is established. The method utilizes properties of the exact solution and leads to final equations that are particularly concise and easy to use.  相似文献   

Bed forms and stratification types of modern gravel meander lobes, Nueces River, Texas     

THOMAS C. GUSTAVSON 《Sedimentology》1978,25(3):401-426

All major streams draining the southwestern flank of the Edwards Plateau in south-central Texas transport large volumes of gravel and sandy muddy gravel and are developing meander lobe sequences consisting predominantly of coarse gravel. The largest of these streams, the Nueces River, has a sinuosity index of 1.3 and an average stream surface slope of 1.8 m/km in the study area. Stream discharge is variable and has ranged from no flow to more than 17,000 m³/s. Mean clast b-axis length for the ten largest clasts at thirteen sample sites ranged from 2.5 to 10.8 cm. Velocities of 2.7-4.4 m/s 1 m above the stream bed are required to transport these clasts. Stream velocities of these magnitudes occur about once in 8 years when discharge of the Nueces River exceeds 3300 m³/s. Mean grain size of Nueces River alluvium ranges from 1.2 to 3.4 cm. At a flow depth of 1 m, sediment of this size has a critical erosion velocity of 1.8-3 m/s. Velocities of this magnitude occur about once in two years when discharge exceeds 340 m³/s. Under these conditions flow is subcritical, with critical shear stresses on depositional surfaces ranging from 6.4 to 12.7 kg/m². Gravel clasts are imbricated and channel bed forms are predominantly transverse gravel bars with slip faces ranging up to 2 m high and wavelengths in excess of 100 m. Stratification includes graded planar crossbeds and horizontal beds. Lower lateral accretion face sediments are also predominantly transverse bars; upper lateral accretion face deposits occur as longitudinal gravel ridges deposited in the lee of vegetation and, less commonly, as chute bars. Near the upper limit of meander lobes where vegetation is heavy, mud and muddy sand occur as overbank deposits; in these deposits sedimentary structures other than desiccation cracks are rare. Sedimentary sequences in gravel meander lobe systems deposited by low sinuosity streams are graded or non-graded horizontal beds and planar cross-beds overlain by mud and muddy sand interbedded with horizontally bedded gravels. Sequences may be several metres thick, but probably do not exceed 8-10 m in thickness. These deposits in turn are overlain by overbank deposits of mud and muddy sand. Similar sedimentary sequences occur in the extensive Quaternary terraces that parallel the Nueces River.  相似文献   

The charge distribution on interstellar grains—The effect of induced charge     

I. C. Simpson  S. Simons  I. P. Williams 《Astrophysics and Space Science》1978,59(2):389-411

A calculation of the equilibrium charge acquired by interstellar grains is given, which takes account of polarization charges that are induced in a grain by incident ions and electrons.Both metal and dielectric grains are considered and photoionization of the latter grains by UV radiation is taken into account where necessary. It is found that the inclusion of the polarization charges in the calculation is only important in gas clouds where the mean charge on a grain is low (<1e); that is, for HI regions and dense molecular clouds. In such clouds, the effect of the polarization charges is to increase the amount of negative charge acquired by a grain. A discussion is given concerning the validity of the classical electrostatic theory employed in the paper for small grains of radius 10^–6 cm, and some astrophysical consequences of the modification of the grain charge by polarization effects are considered.  相似文献   

The evolution of massive close binaries     

De Grève  J. P.  De Loore  C.  Van Dessel  E. L. 《Astrophysics and Space Science》1978,53(1):105-130

The results of evolutionary computations for massive binary systems (initial masses of the primary 10M ) with mass ratios between 0.3 and 0.8 are summarized and compared with observations in order to verify how far one can go with the conservative assumption of mass exchange. It is found that conservative mass exchange leads to acceptable first-order models of W-R and massive X-ray binaries. However, the comparison between this theory and observation reveals that for the observed systems (W-R and X-ray binaries) a preference exists for low intial mass ratios; moreover, the X-ray luminosities of the theoretical models are systematically too low, though this may be due to the adopted wind model. In addition, the influences of several parameters (distance between the components, chemical composition, primary mass, mass ratio and atmosphere) are examined. These parameters influence the remnant mass and any further evolution only marginally. Attention is also given to the effect on the system parameters of a supernova explosion of the remnant of the mass-losing component. For a large range of systems a disruption probability smaller than 25% is found.  相似文献   

Geochemistry and the environment,vol. 1, The Relation of Selected Trace Elements to Health and Disease: A report of a workshop chaired by helen L. cannon. National Academy of Sciences, 1974, 105 pp., $10.00     

J.C. Van Loon 《Geochimica et cosmochimica acta》1978,42(8):1303

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Hydrocarbons in surficial sediments from the Scotian Shelf     

Paul D Keizer  J Dale  D.C Gordon 《Geochimica et cosmochimica acta》1978,42(2):165-172

Surface sediments from 20 stations on the Scotian Shelf, collected on a transect from Halifax to Emerald Bank and around Sable Island, have been analyzed for hydrocarbon content and composition by gas chromatography and fluorescence spectrophotometry. Some samples were taken near abandoned exploratory drilling sites in the Sable Island area. Hydrocarbons appear to be mainly derived from biogenic terrestrial sources as evidenced by an inverse correlation of concentration with increasing distance from the mainland and a strong odd carbon preference in the n-alkanes. Contribution from petroleum sources, while minor, was most noticeable between Halifax and Emerald Bank. There is also evidence that the hydrocarbon composition at abandoned exploratory drilling sites has been slightly altered.  相似文献   

Estuarine chemistry: edited by J. D. Burton and P. S. Liss,Academic Press, 1976, 229 pp., $17.50     

David C. Kurd 《Geochimica et cosmochimica acta》1978,42(2):219

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