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11.
This paper examines the planar dynamics of a wheel-and-spoke configured multi-spacecraft system, connected together by variable length tethers, near the second Sun–Earth Lagrangian point. The closed form solutions of the system under some simple tether length functions are determined and numerical results for the tether pitch librations under more complex tether length functions are obtained, along with the control effort required to maintain the desired tether librations. 相似文献
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Recently, Supernova 2006gy was noted as the most luminous ever recorded, with a total radiated energy of approximately 10(44) Joules. It was proposed that the progenitor may have been a massive evolved star similar to eta Carinae, which resides in our own Galaxy at a distance of about 2.3 kpc. eta Carinae appears ready to detonate. Although it is too distant to pose a serious threat as a normal supernova, and given that its rotation axis is unlikely to produce a gamma-ray burst oriented toward Earth, eta Carinae is about 30,000 times nearer than 2006gy, and we re-evaluate it as a potential superluminous supernova. We have found that, given the large ratio of emission in the optical to the X-ray, atmospheric effects are negligible. Ionization of the atmosphere and concomitant ozone depletion are unlikely to be important. Any cosmic ray effects should be spread out over approximately 10(4) y and similarly unlikely to produce any serious perturbation to the biosphere. We also discuss a new possible effect of supernovae-e-ndocrine disruption induced by blue light near the peak of the optical spectrum. This is a possibility for nearby supernovae at distances too large to be considered "dangerous" for other reasons. However, due to reddening and extinction by the interstellar medium, eta Carinae is unlikely to trigger such effects to any significant degree. 相似文献
15.
Helen E. Mason 《Space Science Reviews》1994,70(1-2):111-114
The CDS and SUMER instruments will make extensive use of spectroscopic diagnostics to determine the physical parameters of the solar transition region and corona. A great deal of effort is going into the development of these techniques to ensure that they are accurate. This requires interfacing solar analysis programs with the best available atomic data calculations. Recent developments in this work will be presented, with specific examples of useful spectral line ratios. 相似文献
16.
Imaging X-ray observations of the Fornax cluster of galaxies centered on NGC 1399 and NGC 1404 are presented. NGC 1399 and NGC 1404, which are separated by about 10 arc minutes, are found to have an unusually high ratio of x-ray to optical flux. We consider the possibility that the x-radiation is produced by hot gas in the cores of the galaxies. Weak X-ray emission is also detected from a point almost exactly mid-way between NGC 1399 and NGC 1404. The combined emission from the galaxies is insufficient by over an order of magnitude to account for the the low-energy X-ray emission detected from this region by the HEAO-l satellite. It is suggested that the bulk of the HEAO-1 source is diffuse gas associated with the cluster as a whole, rather than individual galaxies. 相似文献
17.
Brian J. O'Brien 《Space Science Reviews》1967,7(2-3):293-301
Conclusion A satellite such as Neutral-1 should be instrumented with magnetometers, plasma detectors, and detectors of energetic particles, and flown to an altitude of some 26 R
E in a high-inclination orbit. It can thus probe regions of the magnetosphere of particular importance but as yet unexplored. It also is in an orbit that offers the optimum variety of phenomena to be explored, with the additional advantage that the characteristics of each phenomenon can be compared one with the other and the interrelation of these phenomena deduced. Such a satellite offers unique opportunities to investigate a multitude of unknown phenomena, such as the origin and energization of the particles that cause auroras and constitute Van Allen radiation. It can also potentially yield data to help solve long-lived problems, viz.: do the particles that cause auroras come from the sun, and how does a ripple in the solar corona ultimately feed energy into the magnetosphere at an average rate of 1017-1018 ergs/sec? Someone should fly such a satellite at the earliest opportunity and certainly by sunspot maximum (1969) since the existing satellite and instrumental technology is adequate. 相似文献
18.
Brian A. Tinsley Limin Zhou Weiping Liu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Small changes in the vorticity of winter storms, responding to solar wind variations, are found in winters from 1957 to 2011, and are greater for winters with higher levels of stratospheric volcanic aerosols. Using 1993–2011 data, the response of the vorticity area index (VAI) is shown to be of larger amplitude when the days of minima in the relativistic electron flux (REF) precipitating from the radiation belts are used, instead of heliospheric current sheet (HCS) crossings, as key days in superposed epoch analyses. The HCS crossings mostly occur within a few days of the REF minima. The VAI is an objective measure of the area of high cyclonic vorticity, and for the present work is derived from ERA-40 and ERA-Interim reanalyses of global meteorological data. The VAI dependencies on the stratospheric aerosol content (SAC) and the REF are consistent with a model in which the ionosphere-earth current density (Jz) affects cloud microphysics. One of the ways in which Jz is modulated is by changes in stratospheric column resistance (S), which is increased by stratospheric aerosols. Because S is in series with the tropospheric column resistance (T), Jz modulation by REF requires that S be not negligible with respect to T. So the Jz modulation and the VAI response appear when the SAC is very high, or the REF reductions (which also increase S) are very deep, and when the product of the SAC and the reciprocal of the REF exceeds a threshold value dependent on T. 相似文献
19.
Johnson R. L. Mason J. L. Petrou N. V. Woll H. J. Hansen G. L. Regan D. C. 《IEEE transactions on aerospace and electronic systems》1966,(1):121-136
A panel session held at the 1965 Aerospace Conference, Houston,Tex., June 23, 1965. Panelists discussed Life-Suppport interfaces with Electric Power; Communications; Navigation; System Integration for Future Space Programs; and Reliability. 相似文献
20.
Margarita Karovska Brian E. Wood John W. Cook Russell A. Howard Guenter E. Brueckner 《Space Science Reviews》1999,87(1-2):219-222
We present the results from a study of the dynamical properties of polar jets in the Sun's polar regions using LASCO C2 coronagraph
and EIT observations. In the simplest impulsive acceleration scenarios for jets, gravity is expected to be the dominant force
on the jet following the initial acceleration, especially in the Sun's polar regions where the open magnetic fields should
not significantly impede the jet's motion. Our analysis shows that although at low heights the kinematics of the jets could
be consistent with a gravitational deceleration of the ejected plasma, at higher heights their motions may simply follow the
ambient solar wind outflow. If so, the polar jets can be used as tracers of the solar wind in coronal holes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献