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Srinivas N. Mohan 《Icarus》1979,40(2):317-330
The global distribution of existing lunar topography suffers from a lack of measurements of far-side radii because of the sparsity of data types in the nonequatorial regions. This paper presents determinations of far-side lunar radii based on the reduction of photogrammetric measurements derived from selected Apollo 16 trans-Earth phase photographs. The regions covered in this analysis lie west of Mare Moscoviense between longitudes 90 and 130°E and latitudes 10 and 60°N. The determinations are made using control points appearing on both NASA topographic orthophoto maps and the Apollo 16 photographs. The estimated lunar radii are referred to these control points and determined with a relative accuracy of 500 m. The new lunar radii are used to generate a topographic map covering the area investigated. The map shows that, with the given spatial density of surface festures measured, basin-sized features can be resolved. In particular, the far-side craters Fabry, Riemann, and Szilard comprise a topographically depressed region about 500 km in diameter centered at 120°E and 38.5°N. The floor of this basin is 2.4 to 3.4 km below the reference sphere of 1738.0 km and 4.8 to 5.8 km below the northern rim of the basin. A comparison of the depth of the unfilled basin with the depths of maria-filled front-side basins leads to the conclusion that basalt fill of the near-side maria may be 2 km deep. The topographic map shows good correlation with geologic provinces of young plains and cratered terra in the far-side highland region investigated. Lack of correlation between sampled values of the state-of-the-art 16th-order and 16th-degree harmonic gravity field model and corresponding topographical values leads to the conclusion that the far-side region investigated is isostatically compensated.  相似文献   

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The behavior of dispersive Alfvén waves (DAWs), including inertial and kinetic Alfvén waves, in astrophysical plasmas of very low, intermediate, and low pressure is investigated in the hydrodynamic approximation. New full solutions are obtained. Our results are analyzed and compared with those from the kinetic approach. It is shown that one general solution for the DAWs in plasmas of very low, intermediate, and low pressure can be obtained in the framework of the hydrodynamic approach, as opposed to the kinetic one. In the very low damping region, the kinetic and hydrodynamic solutions agree very well; but there are parameter regions where the solutions are essentially different. The influence of the astrophysical medium parameters on the DAW behavior and properties is analyzed. All main wave characteristics—the dispersion, damping, polarization, density perturbations, and charge density perturbations—are obtained, whose the consideration is very important for the observation and detection of these waves, as well as for a more correct understanding of their behavior and role in various astrophysical processes taking place in the cosmic medium.  相似文献   

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The work is devoted to the study of the behavior of dispersive Alfvén waves, including inertial and kinetic Alfvén waves, in astrophysical plasma of very low, intermediate, and low pressure. New and full solutions were obtained. The solutions for “ordinary” and inertial Alfvén waves were shown to be particular cases of the general solution. The effect of the parameters of the astrophysical medium on the behavior and properties of dispersive Alfvén waves was analyzed. All the main wave characteristics were obtained, namely, the dispersion, fading, polarization, density perturbations, and charge density perturbations, whose consideration is essential for observation and detection of these waves and for more adequate understanding of their role in different astrophysical processes that occur in the space environment.  相似文献   

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As a result of an error by the authors,in the paper"The Lyman-alpha Solar Telescope(LST)for the ASO-S Mission.I.Scientific Objectives and Overview"by Hui Li et al.(RAA 2019 Vol.19,No.11,158,doi:10.1088/1674C4527/19/11/158),there is an error occurred in Table 2 about the image size of SCI UV in the'Event'mode:the image size 4608×4608 should be replaced by 2048×2048.This correction is indicated in bold face in the following table.  相似文献   

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