We present the processing results of slitless chromospheric spectra in a D3 helium line obtained during the solar eclipse of March 29, 2006. A “Cascade-Photometrics 650” CCD matrix photodetector with
a rate of 16 frames/s was used for the observations. Altitude distribution of absolute brightness of the helium chromosphere
has been mapped in a latitude interval 30 N-10 S on the western limb. A correlation between absolute brightness of the helium
chromosphere and a solar cycle phase has been confirmed. It has been revealed that the altitude distribution of helium emission
has one maximum at an altitude of approximately 2000 km. In the lower chromosphere, helium emission is undetectable. This
confirms our assumption about absence of an additional maximum at 300 km in the D3 line brightness distribution in the chromosphere during sunspot maximum periods. The results also prove that X-ray coronal
radiation with λ < 6 nm is the source of helium excitation in the lower chromosphere. 相似文献
We examine the formation patterns of the low-water periods 1976?C1982 and 1996?C2011 for the Selenga river. One of the immediate reasons for the low-water periods under consideration is the attenuation of the circulation in the zone of convergence of monsoon flows and mid-latitude flows over Mongolia and North China. Unlike the low-water periods of the preceding decades, a decrease in precipitation amounts during the current low-water period is taking place concurrently with large-scale climatic changes. 相似文献
Here we present new data from a systematic Sr, Nd, O, C isotope and geochemical study of kimberlites of Devonian age Mirny field that are located in the southernmost part of the Siberian diamondiferous province. Major and trace element compositions of the Mirny field kimberlites show a significant compositional variability both between pipes and within one diatreme. They are enriched in incompatible trace elements with La/Yb ratios in the range of (65–300). Initial Nd isotope ratios calculated back to the time of the Mirny field kimberlite emplacement (t = 360 ma) are depleted relative to the chondritic uniform reservoir (CHUR) model being 4 up to 6 ɛNd(t) units, suggesting an asthenospheric source for incompatible elements in kimberlites. Initial Sr isotope ratios are significantly variable, being in the range 0.70387–0.70845, indicating a complex source history and a strong influence of post-magmatic alteration. Four samples have almost identical initial Nd and Sr isotope compositions that are similar to the prevalent mantle (PREMA) reservoir. We propose that the source of the proto-kimberlite melt of the Mirny field kimberlites is the same as that for the majority of ocean island basalts (OIB). The source of the Mirny field kimberlites must possess three main features: It should be enriched with incompatible elements, be depleted in the major elements (Si, Al, Fe and Ti) and heavy rare earth elements (REE) and it should retain the asthenospheric Nd isotope composition. A two-stage model of kimberlite melt formation can fulfil those requirements. The intrusion of small bodies of this proto-kimberlite melt into lithospheric mantle forms a veined heterogeneously enriched source through fractional crystallization and metasomatism of adjacent peridotites. Re-melting of this source shortly after it was metasomatically enriched produced the kimberlite melt. The chemistry, mineralogy and diamond grade of each particular kimberlite are strongly dependent on the character of the heterogeneous source part from which they melted and ascended.
The formation of fast ice in the costal zone of freezing seas (immobile ice) is considered on the basis of a specially developed
thermodynamic model that takes into account the energy exchange in the atmospheric boundary layer and the salinification of
the water layer under the ice. The conditions at which the wind forced onshore motion of the ice under the influence of the
wind stress at the ice’s surface is possible are studied using the example of the Baidaratskaya Guba in the Kara Sea. 相似文献
We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties. In the first pollution scenario, the oil product was introduced into wet river sand, and in the second case, dry sand was contaminated by the oil product and was then moistened with water. By considering these two scenarios as multicomponent dispersion systems with varying degrees of contamination and humidity, and by using a polystructural granular model with pore spaces and closed inclusions, we calculated that the heat conductivity of the sandy soil increased under the first pollution scenario and decreased under the second, but the change in the volumetric heat capacity of the sandy soil was proportional only to the amount of oil pollution, not the manner in which it was introduced. We also determined the temperature dependencies of these two thermophysical properties of sandy soil when polluted by oil, of which information will be useful for future containment and remediation of oil-contaminated soil. 相似文献
Harmonic coefficients of the 2nd degree are separated into the invariant quantitative (the 2nd-degree variance) and the qualitative
(the standardized harmonic coefficients) characteristics of the behavior of the potential V2(t). On this basis the evolution of the Earth's dynamical figure is described as a solution of the time-dependent eigenvalues–eigenvectors
problem in the canonical form. Such a canonical quadratic form is defined only by temporal variations of the harmonic coefficients
and always remains finite, even within an infinite time interval. An additional condition for the correction or the determination
of temporal variations of the 2nd degree is obtained. Temporal variations of the fully normalized sectorial harmonic coefficients
are estimated in addition to ˙Cˉ20, ˙Cˉ21, and ˙Sˉ21 of the EGM96 gravity model. In addition, a non-linear hyperbolic model for Cˉ2m(t), Sˉ2m(t) is constructed. The trigonometric form of the hyperbolic model leads to the consideration of the potential V2(ψ) instead of V2(t) within the closed interval −π/2≤ψ≤+π/2. Thus, it is possible to evaluate the global trend of V2(t), the Earth's principal axes and the differences of the moments of inertia within the whole infinite time interval.
Received: 25 September 1998 / Accepted: 28 June 2000 相似文献
In the northern Barents Sea Opening (BSO) the K1 tidal energy is predominant in the diurnal tidal frequency band, suggesting the generation of a topographic wave with the K1 tidal frequency. Tidal energy of the K1 component becomes strong where bottom topography undulates in the BSO and the scale of the undulation is close to the wavelength of the K1 wave. An analytical model is developed to investigate the energy enhancement mechanism of the tidally induced topographic wave due to a resonance between tidal current, a topographic wave and periodic topography. The wave excited by the resonance is identified as a resonant double Kelvin wave (DKW) and the significant K1 energy in the BSO could be due to the excitation of the resonant DKW. 相似文献