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961.
The bulk viscosity is introduced into the frame of ordinary Friedmannian cosmology (under highly idealized assumption of the constant coefficient of bulk viscosity). Explicit solutions are given for the viscous flat universe filled with the dust-substratum and for the viscous radiative universe. The problem, how does the introduction of viscosity affect the appearance of singularity, is briefly discussed. 相似文献
962.
Atoms which escape Titan's atmosphere are unlikely to possess escape velocity from Saturn, and can orbit the planet until lost by ionization or collision with Titan. It is predicted that a toroidal ring of between ~1 and ~103 atoms or molecules cm?3 exists around Saturn at a distance of about 10 times the radius of the visible rings. This torus may be detectable from Earth-orbit and detection of nondetection of it may provide some information about the presence or absence of a Saturnian magnetic field, and the exospheric temperature and atmospheric escape rate of Titan. It is estimated that, if Titan has a large exosphere, ~97% or more of the escaping atoms can be recaptured by Titan, thereby decreasing the effective net atmospheric loss rate by up to two orders of magnitude. With such a reduction in atmospheric loss rates, it becomes more plausible to suggest that satellites previously thought too small to retain an atmosphere may have one. It is suggested that Saturn be examined by Lyman-α and other observations to search for the gaseous torus of Titan. If successful, these could then be extended to other satellites.The effect of a hypothetical Saturnian magnetosphere on the atmosphere of Titan is investigated. It is shown that, if Saturn has a magnetic field comparable to Jupiter's (~10 G at the planetary surface), the magnetospheric plasma can supply Titan with hydrogen at a rate comparable to the loss rates in some of the models of Trafton (1972) and Sagan (1973). A major part of the Saturnian ionospheric escape flux (~ 1027 photoelectrons sec?1) could perhaps be captured by Titan. At the upper limit, this rate of hydrogen input to the satellite could total ~0.1 atm pressure over the lifetime of the solar system, an amount comparable to estimates of the present atmospheric pressure of Titan. 相似文献
963.
Computations of the equivalent widths of absorption lines as a function of planetary phase angle are made for a homogeneous cloud with particles having the properties (shape, refractive index, and size distribution) deduced from polarimetry of Venus. The computed equivalent widths show an “inverse phase effect” comparable to that which is observed for CO2 lines on Venus. This result verifies a recent suggestion of Regas et al. that the existence of an inverse phase effect does not by itself imply the presence of multiple layers of scattering particles in the atmosphere of Venus. 相似文献
964.
From riometer records for the sudden impulse event of 4 February 1969, it is shown that ionospheric absorption accompanying a sudden impulse has the same type of latitude and longitude variations found for sudden commencement events. In addition, an examination of magnetograms at College, Alaska shows that some positive sudden impulses may trigger negative bays around local midnight, similar to the recent results for sudden commencements. 相似文献
965.
M. Rousseau 《Planetary and Space Science》1973,21(10):1705-1712
Atmospheric densities between 1500 and 3000km have been determined from observations of satellites with large surface to mass ratios. The analysis has been made for optimum periods where the satellite is continuously in sunlight and when the effects of Earth albedo are minimum. Twenty six values of density obtained from 1965 to 1970 have been analysed. 相似文献
966.
The radio structure of the active region McMath 11976 has been investigated with an east-west resolution of 16″ at a wavelength of 2.8 cm. Six bright components were found with angular sizes of the order of 20″. From the position measure of these components in two following days the heights above the solar photosphere are determined. Their positions are compared with the Hα and magnetic structure of the active region. The derived brightness temperatures reach unusual values, up to 6 × 106K for the brightest component. 相似文献
967.
Arch M. Reid 《Earth, Moon, and Planets》1974,9(1-2):141-146
Several investigators have attempted, from studies of lithic fragments and/or glasses, to determine the types of rocks that constitute the parent materials of lunar highland soils. Comparing only major element data, and thus avoiding the problems induced by individual classifications, these data appear to converge on a relatively limited number of rock types. The highland soils are derived from a suite of highly feldspathic rocks comprising anorthositic gabbros (or norites), high alumina basalts, troctolites, and less abundant gabbroic (or noritic) anorthosites, anorthosites and KREEP basalts. 相似文献
968.
K.M. Merrill 《Icarus》1974,23(4):566-567
Spectrophotometry of Comet Kohoutek (1973f) covering the wavelength range 8–13 μm is presented. The spectral shape of the derived flux excess above a blackbody closely resembles that seen in circumstellar and interstellar dust and generally attributed to metallic silicates. 相似文献
969.
Slitless spectrograms obtained during the eclipse of 10 June 1972 have been analyzed to determine the height distribution of the D3 He line intensity.For undisturbed regions the maximum of D3 line intensity is confirmed to exist at about 1700km above the limb. Besides the above mentioned maximum, in plages a considerable intensity may be observed at low heights (h < 1000 km).An analysis of these observations for h > 1000 km has been carried out within the low temperature mechanism of triplet helium emission taking into account the helium ionization by XUV radiation. The density dependence of the 23
S level population at different XUV flux values has been calculated. Our observations give N
e 2 × 1010 cm–3 in the chromosphere at h = 2000 km. The probable coincidence of the H and He emission small filaments in the middle chromosphere is discussed. 相似文献
970.
Relationship between the geoefficiency of the solar flares as well as of the active regions passing the central meridian of the Sun and the configuration of the large scale solar magnetic field is studied.It is shown that if the tangential component of the large scale magnetic field at the active region or at the flare region is directed southwards, that region and that flare produce geomagnetic storm. In case when the tangential magnetic field is directed northward, the active region and the flares occurring at that region do not cause any geomagnetic disturbance.An index of the geoefficiency of the solar flares and of the active regions is proposed. 相似文献