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521.
Enclosure of some portion of one or more natural stream-drainage basins by superposition of a rectangle on a map of drainage network results in fragmentation of the natural basins into a set of disjoint channel networks. Each of these may have some channel links and forks of the natural network plus truncated links intersected by the enclosure boundary. The topological properties of the network elements in the enclosure are used to set up a model of random network patterns, in which the number of disjoint channel networks is expressed as a function of the number of links and forks in the enclosures. This function is shown to be a multiplicative constant times the square root of the number of links or forks. Empirical data on square and rectangular enclosures of several sizes from the Inez (Kentucky)Quadrangle map showed that the predicted multiplicative constants do not agree with observation, but that the square-root relation seems to hold at least to a first approximation. The models thus can be used as a norm against which deviations of real-world enclosures from network pattern randomness can be studied. 相似文献
522.
Summary. A new set of 1×1° mean free-air anomalies in the Indian Ocean is determined on the basis of previously published free-air anomaly maps (Talwani & Kahle) and the most recent Lamont surface ship gravity measurements. The data are then used to compute a (total) 1×1° gravimetric Indian Ocean geoid. The computation is carried out by combining the Goddard Space Flight Center (GSFC) GEM-6 geoid and a difference geoid that corresponds to the differences between the set of 1×1° surface gravity values and the GEM-6 gravity anomalies. The difference geoid is highest over the Madagascar Ridge (+ 20 m) and lowest over the Timor Trough (-30 m). The total geoid is compared with GEOS-3 radar altimeter derived geoid profiles and geophysical implications are discussed. 相似文献
523.
524.
Michael D. Moutsoulas 《Earth, Moon, and Planets》1973,8(3):392-430
The measured and calibrated coordinates of selenodetic control points on 35 Pic-du-Midi negatives obtained by the method of star-calibrated lunar photography (cf. Moutsoulas, 1970) are presented in this paper.Paper dedicated to Professor H. C. Urey on the occasion of his 80th birthday on 29 April 1973.Work supported under Contract F 61052-68-C-0002 and Grant AFOSR-72-2261 between the Aerospace Office of Scientific Research, U.S. Air Force, and the University of Manchester in England. 相似文献
525.
526.
Michael Longuet-Higgins 《Dynamics of Atmospheres and Oceans》1982,7(1):33-46
Long range acoustic soundings with triads of transducers can determine accurately the vorticity integrated over the corresponding triangular areas of the ocean. However, for a given number n of transducers not all such observations are independent. In this note we show, first, that the number N of possible independent observations is in fact N = (n ? 1) (n ? 2)/2 Secondly, we shall show such observations are in principle able to provide estimates of the vorticity field and its derivatives up to order m = (n ? 3). Thus four transducers yield an accurate estimate of the scalar vorticity ω and its horizontal gradient δ ω, while five transducers will yieldalso the Laplacian δ2ω. 相似文献
527.
528.
Michael C. Kelley 《Planetary and Space Science》1976,24(4):355-357
The average auroral zone electric field pattern has been studied to determine whether such fields can, as has been suggested, drive the super-rotation of the upper atmosphere. It is shown that the local time averaged meridional electric field is small and, in fact, poleward, which would tend to drive a prevailing westerly wind. When averaged only over the dayside, where ion drag should be most important due to the higher ion density, the poleward average is even more pronounced. Thus at high latitudes ion drag acts to drive a prevailing neutral wind to the west. Model calculations indicate that without including electric fields the prevailing wind at mid-latitudes should be to the west, due to higher ion drag on the dayside. Including the present results will increase ion drag on the dayside and further enhance this effect. These results thus suggest that at middle and high latitudes the upper atmosphere does not superrotate. 相似文献
529.
530.
Density, bulk-velocity, and heat-flow moments are calculated for truncated maxwellian distributions representing the cool and hot populations of solar-wind electrons, as realized at the base of a hypothetical exosphere. The electrostatic potential is thus calculated by requiring charge quasineutrality and the absence of electrical current. Plasma-kinetic coupling of the cool-electron and proton bulk velocities leads to an increase in the electrostatic potential and a decrease in the heat-flow moment. If the velocities differ by the Alfvén speed along the magnetic field, for example, the potential rises to 72.6 V and the heat flux falls to 2.72×10–2 erg cm–2 s–1. In each case the heat flux is carried mainly by the quasi-exospherichot electrons. 相似文献