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901.
K. Papadopoulos J. G. Lyon C. C. Goodrich P. J. Cargill A. S. Sharma R. Kulkarni CL. L. Chang A. Mankofsky 《Space Science Reviews》1995,71(1-4):671-690
The objective of the University of Maryland ISTP theory project is the development of the analytical and computational tools, which, combined with the data collected by the space and ground-based ISTP sensors, will lead to the construction of the first causal and predictive global geospace model. To attain this objective a research project composed of four complementary parts is conducted. First the global interaction of the solar wind-magnetosphe re system is studied using three-dimensional MHD simulations. Appropriate results of these simulations are made available to other ISTP investigators through the Central Data Handling Facility (CDHF) in a format suitable for comparison with the observations from the ISTP spacecrafts and ground instruments. Second, simulations of local processes are performed using a variety of non-MHD codes (hybrid, particle and multifluid) to study critical magnetospheric boundary layers, such as the magnetopause and the magnetotail. Third, a strong analytic effort using recently developed methods of nonlinear dynamics is conducted, to provide a complementary semi-empirical understanding of the nonlinear response of the magnetosphere and its parts to the solar wind input. The fourth part will be conducted during and following the data retrieval and its objective is to utilize the data base in conjunction with the above models to produce the next generation of global and local magnetospheric models. Special emphasis is paid to the development of advanced visualization packages that allow for interactive real time comparison of the experimental and computational data. Examples of the computational tools and of the ongoing investigations are presented. 相似文献
902.
C. T. Russell R. C. Snare J. D. Means D. Pierce D. Dearborn M. Larson G. Barr G. Le 《Space Science Reviews》1995,71(1-4):563-582
The magnetometer on the POLAR Spacecraft is a high precision instrument designed to measure the magnetic fields at both high and low altitudes in the polar magnetosphere in 3 ranges of 700, 5700, and 47000 nT. This instrument will be used to investigate the behavior of fieldaligned current systems and the role they play in the acceleration of particles, and it will be used to study the dynamic fields in the polar cusp, magnetosphere, and magnetosheath. It will measure the coupling between the shocked magnetosheath plasma and the near polar cusp magnetosphere where much of the solar wind magnetosphere coupling is thought to take place. Moreover, it will provide measurements critical to the interpretation of data from other instruments. The instrument design has been influenced by the needs of the other investigations for immediately useable magnetic field data and high rate (100+vectors s–1) data distributed on the spacecraft. Data to the ground includes measurements at 10 vectors per second over the entire orbit plus snapshots of 100 vectors per second data. The design provides a fully redundant instrument with enhanced measurement capabilities that can be used when available spacecraft power permits. 相似文献
903.
Forestieri A.F. Baraona C.R. 《IEEE transactions on aerospace and electronic systems》1984,(6):666-671
A Space Station Task Force was established by NASA in May 1982 to provide focus and direction for space station planning activities. The Task Force also provides Congress and the Administration with sufficient information to allow them to make an informed decision on whether the United States should proceed with a space station as the next major national initiative in space. This paper presents the status of planning activities to date, with major emphasis on the power system, and discusses technology options, power requirements, and schedule. 相似文献
904.
We present preliminary results of multicolor CCD imaging within the error boxes of several unidentified faint galactic X-ray sources. New, faint ultraviolet stars have been found lying within the combined SAS-3/HEAO A-3 error boxes of Reid et al. (1980) for 0918-549, 1822-000 and the X-ray burster 1905+000.Based on observations collected at the European Southern Observatory, La Silla, Chile.Visiting Astronomer, Canada-France-Hawaii Telescope, administered by NRC of Canada, CNRS of France and U. of Hawaii 相似文献
905.
J. Schrijver A. C. Brinkman H. van der Woerd M. G. Watson A. R. King J. van Paradijs M. van der Klis 《Space Science Reviews》1985,40(1-2):121-126
We report results from EXOSAT observations of the intermediate polar system 2A0526-328 (TV Col). The hard X-ray emission (2–8 keV) is modulated with a period of 1943 s, interpreted as the white-dwarf rotation period. Soft and hard X-ray emission show intensity minima, in phase with the orbital period of 0.2286 days; analysis of the hard X-ray spectra shows that these minima are caused by an extra low-energy absorption corresponding to a H column density of 4 × 1022 cm-2. 相似文献
906.
We review results of correlated IR, optical and X-ray observations of GX 339-4 made from March 1981 through May 1984. In the soft X-ray state, the object does not show outstanding optical and X-ray variability. Night-to-night smooth optical variations of 0.3 magnitudes were however present during one observing run. In contrast, the hard X-ray state is characterised by strong erratic optical and X-ray fluctuations on time scales from 20 milliseconds to seconds, as well as 7 to 20 second quasi-periodic oscillations. The optical counterpart appears much redder in the IR during the hard state. Particular attention is drawn to the hard to soft X-ray transition which occured in June 1981. The shape of the IR to X-ray energy distribution is discussed. The unusual features of this black hole candidate are examined in the framework of the current theories of accretion.Based partly on observations obtained at the European Southern Observatory, La Silla, Chile. 相似文献
907.
Y. C. Whang 《Space Science Reviews》1991,57(3-4):339-388
Observations of plasma and magnetic fields by Pioneer 10 and 11 and Voyager 1 and 2 reveal that MHD shocks are an important component of the large-scale solar wind structures in the outer heliosphere. This review discusses recent progress in simulation studies of the nonlinear evolution of the solar wind structures, and in particular concentrates on the theoretical development and applications of the shock interactions model. Various stream propagation models, which do not use the Rankine-Hugoniot relations to calculate the jump conditions at shock crossings, have been used to simulate the essential evolution process of isolated streams and the formation and propagation of corotating and transient shocks. They produce fairly good results in the region up to a few AU. In 1984, the shock interactions model was introduced to study the evolution of large-scale solar wind structures in the region outside 1 AU up to several tens of AU. The model uses the exact Rankine-Hugoniot relations to calculate the shock speed and shock strength at all shock crossings. So that the model can more accurately calculate the shock speeds and the accumulated irreversible shock heating of plasma at several tens of AU. The applications of the shock interactions model are presented in three groups. (a) The first group covers the basic interaction of a shock with the ambient solar wind, the formation and propagation of shock pairs, and the collision and merging of shocks. (b) The second group covers the use of the shock interactions model to simulate the nonlinear evolution of large-scale solar wind structures in the outer heliosphere. These simulation results can provide the detailed evolution process for large-scale solar wind structures in the vast region not directly observed. Two selected studies are reported. (c) Finally, the shock interactions model is applied to studying the heating of the solar wind in the outer heliosphere. The model calculations support shocks being chiefly responsible for the heating of the solar wind plasma in the outer heliosphere at least up to 30 AU. 相似文献
908.
A knowledge-based system for air traffic control (ATC) in terminal control regions is designed for improving service and operation. Domain knowledge is established following rules, regulations, and comments from controllers. An expert system is adopted for approach control and airport control in the terminal control region. The proposed system was implemented in PC-AT with Turbo Prolog. The air terminal control monitor was checked with regard to flight information input, real-time data refreshment, air traffic rescheduling, constraint violation double checking, emergency responses, and normal monitoring. Simulation results are given 相似文献
909.
The signal format and spectral properties of the 406-MHz emergency locator transmitter (ELT) used in the search and rescue satellite aided tracking (SARSAT) system are examined. The ELT improves location estimate accuracies and can relay information about the particular aircraft and its problem, by means of the digitally modulated message fields. It is shown that due to the RF signal frequency characteristics and the Doppler shift, processing must be performed over a frequency band of approximately 25 kHz. Through the use of the fast Fourier transformation (FFT), the frequency spectrum of the ELT is analyzed, taking account of effects due to noise, multiple simultaneously received signals, and Doppler shift. It is demonstrated that the FFT provides an effective means for detecting and recognizing the presence of one or more ELT signals over this 25-kHz frequency band. Some recommendations are made to improve the spectral characteristics and the performance of the ELT 相似文献
910.
C. De Jager 《Space Science Reviews》1975,17(5):645-654
A review is given of the solar radiation between wavelengths of approx. 5 m. and 1 mm. After discussing the astrophysical background (Section 2), we review the brightness temperatures measured in the continuous spectrum in the disk center (Section 3), and compare them with model predictions. The observed limb darkening (or brightening) is described in Section 4, and the line spectrum in Section 5. In Section 6 considerations are given on the usefulness of infrared observations for the investigation of small structures on the Sun. 相似文献