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751.
Richard G. Lugar 《Space Policy》1985,1(3):231-236
Senator Lugar argues that a better European appreciation of the SDI is essential to try to define the roles of the US allies in the programme. A number of guidelines for allied participation should be applied, covering mode of participation, areas for participation, responsibilities under treaty provisions, technology transfer and security safeguards. Bilateral agreements are viewed as the mode for proceeding, but it is incumbent on the US government to outline the next steps it evisages to come to grips with the political considerations that will influence allied calculations on whether and under what circumstances to participate in SDI research. 相似文献
752.
T.J. Stuchi T. Yokoyama A.A. Corrêa R.H. Solórzano D.M. Sanchez S.M.G. Winter O.C. Winter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The problem of a spacecraft orbiting the Neptune–Triton system is presented. The new ingredients in this restricted three body problem are the Neptune oblateness and the high inclined and retrograde motion of Triton. First we present some interesting simulations showing the role played by the oblateness on a Neptune’s satellite, disturbed by Triton. We also give an extensive numerical exploration in the case when the spacecraft orbits Triton, considering Sun, Neptune and its planetary oblateness as disturbers. In the plane a × I (a = semi-major axis, I = inclination), we give a plot of the stable regions where the massless body can survive for thousand of years. Retrograde and direct orbits were considered and as usual, the region of stability is much more significant for the case of direct orbit of the spacecraft (Triton’s orbit is retrograde). Next we explore the dynamics in a vicinity of the Lagrangian points. The Birkhoff normalization is constructed around L2, followed by its reduction to the center manifold. In this reduced dynamics, a convenient Poincaré section shows the interplay of the Lyapunov and halo periodic orbits, Lissajous and quasi-halo tori as well as the stable and unstable manifolds of the planar Lyapunov orbit. To show the effect of the oblateness, the planar Lyapunov family emanating from the Lagrangian points and three-dimensional halo orbits are obtained by the numerical continuation method. 相似文献
753.
E.G. Shelley 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(4):401-410
Energetic ion composition measurements have now been performed from earth orbiting satellites for more than a decade. As early as 1972 we knew that energetic (keV) ions of terrestrial origin represented a non-negligible component of the storm time ring current. We have now assembled a significant body of knowledge concerning energetic ion composition throughout much of the earth's magnetosphere. We know that terrestrial ions are a common component of the hot equatorial magnetospheric plasma in the ring current and the plasma sheet out to ? 23 RE. During periods of enhanced geomagnetic activity this component may become dominant. There is also clear evidence that the terrestrial component (specifically O+) is strongly dependent on solar cycle. Terrestrial ion source, transport, and acceleration regions have been identified in the polar auroral region, over the polar caps, in the magnetospheric boundary layers, and within the magnetotail lobes and plasma sheet boundary layer. Combining our present knowledge of these various magnetospheric ion populations, it is concluded that the primary terrestrial ion circulation pattern associated with enhanced geomagnetic activity involves direct injection from the auroral ion acceleration region into the plasma sheet boundary layer and central plasma sheet. The observed terrestrial component of the magnetospheric boundary layer and magnetotail lobes are inadequate to provide the required influx. They may, however, contribute significantly to the maintenence of the plasma sheet terrestrial ion population, particularly during periods of reduced geomagnetic activity. It is further concluded, on the basis of the relative energy distributions of H+ and O+ in the plasma sheet, that O+ probably contributes significantly to the ring current population at energies inaccessible to present ion composition instrumentation (? 30 keV). 相似文献
754.
The roll manoeuvre of SOHO on September 3, 1997 provided the opportunity to study the northern coronal hole with SUMER slits
in east-west orientation, so that polar plumes and inter-plume lanes could be observed simultaneously. A preliminary analysis
of the observations shows that lines emitted by ions with the lowest formation temperatures (with the exceptions of Ne7+ and Ar7+) have the largest ratios of plume to lane radiances at heights between 35 000 km and 70 000 km above the photosphere. All
lines have narrower widths inside plumes than outside. Electron densities have been deduced in plumes and lanes from Si VIII
and Mg VIII line radiance ratios. The Mg IX pair was used to determine the corresponding electron temperatures. Neon (with
a high first-ionization potential) is found to be less abundant relative to magnesium (with low FIP) in a plume compared to
an inter-plume lane, but the variation is smaller than previously determined Ne/Mg abundance ratios in a plume relative to
the photosphere.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
755.
R.E. Hartle 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(4):321-332
The Voyager 1 measurements made during the Titan flyby reveal that Saturn's rotating magnetospheric plasma interacts directly with Titan's neutral atmosphere and ionosphere. This results from the lack of an intrinsic magnetic field at Titan. The interaction induces a magnetosphere which deflects the flowing plasma around Titan and forms a plasma wake downstream. Within the tail of the induced magnetosphere, ions of ionospheric origin flow away from Titan. Just outside Titan's magnetosphere, a substantial ion-exosphere forms from an extensive hydrogen-nitrogen exosphere. The exospheric ions are picked up and carried downstream into the wake by the plasma flowing around Titan. Mass loading produced by the addition of exospheric ions slows the wake plasma down considerably in the vicinity of the magnetopause. 相似文献
756.
G.D. Aburjania L.S. Alperovich A.G. Khantadze O.A. Kharshiladze 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(4):624-627
The paper presents a physical mechanism of large-scale vortex electric field generation in the ionospheric E- and F-layers. It shows that the planetary-scale, synoptic short-period (from several second to several hours) and fast processes (with propagation velocity higher than 1 km/s) produce a planetary-scale internal vortex electric field. Its value may far exceed that of the dynamo-field generated in the same ionospheric layer by local wind motion. We found, that an ionospheric source of the vortex electric field is spatial inhomogeneity of the geomagnetic field. 相似文献
757.
The results of experimental and numerical investigations of resonant vibration frequencies and modes for rectangular cantilever plates of constant thickness are presented. The investigations are carried out using the methods of interference holography and finite elements, and the results may serve as basic references in determining resonant frequencies and modes of compressor and turbine blade vibrations. 相似文献
758.
An iteration method for airfoil shape completing using the pressure coefficient distribution specified on its sought part is proposed. The incompressible flow viscosity is taken into account by the boundary layer model, the iteration process is constructed with the use of G.Yu. Stepanov’s idea. The solution algorithm is compiled and a set of numerical calculations is carried out. It is shown that the method proposed offers advantages over the well-known numerical-analytical scheme of solving mixed inverse boundary-value problems of aerohydrodynamics in the case of viscous incompressible fluid. 相似文献
759.
As we resolve ever smaller structures in the solar atmosphere, it has become clear that magnetism is an important component of those small structures. Small-scale magnetism holds the key to many poorly understood facets of solar magnetism on all scales, such as the existence of a local dynamo, chromospheric heating, and flux emergence, to name a few. Here, we review our knowledge of small-scale photospheric fields, with particular emphasis on quiet-sun field, and discuss the implications of several results obtained recently using new instruments, as well as future prospects in this field of research. 相似文献
760.
F. Bocchino R. Bandiera Y. Gallant 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(3):407-410
The investigation of the general properties of non-thermal (NT) X-ray shell supernova remnants (SNRs), of which SN 1006 is the prototype, is important to understand how electrons are accelerated in SNR shocks and what is the origin of cosmic rays. Using the XMM-Newton satellite, we are carrying on a survey of putative non-thermal SNR candidates previously unknown or little studied in the X-ray band, in order to investigate the different manifestations of NT emission in SNR shells. The SNRs we have selected are likely to expand in a low density medium, and therefore to have a low thermal X-ray emission, that usually outshines the non-thermal one. We report here preliminary results obtained on the SNR shell DA 530. 相似文献