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排序方式: 共有244条查询结果,搜索用时 718 毫秒
71.
L. Eliasson O. Norberg R. Lundin K. Lundin S. Olsen H. Borg M. André H. Koskinen P. Riihelä M. Boehm B. Whalen 《Space Science Reviews》1994,70(3-4):563-576
The Hot Plasma Experiment, F3H, on boardFreja is designed to measure auroral particle distribution functions with very high temporal and spatial resolution. The experiment consists of three different units; an electron spectrometer that measures angular and energy distributions simultaneously, a positive ion spectrometer that is using the spacecraft spin for three-dimensional measurements, and a data processing unit. The main scientific objective is to study positive ion heating perpendicular to the magnetic field lines in the auroral region. The high resolution measurements of different positive ion species and electrons have already provided important information on this process as well as on other processes at high latitudes. This includes for example high resolution observations of auroral particle precipitation features and source regions of positive ions during magnetic disturbances. TheFreja orbit with an inclination of 63° allows us to make detailed measurements in the nightside auroral oval during all disturbance levels. In the dayside, the cusp region is covered during magnetic disturbances. We will here present the instrument in some detail and some outstanding features in the particle data obtained during the first months of operation at altitudes around 1700 km in the northern hemisphere auroral region. 相似文献
72.
Hannes Alfvén 《Space Science Reviews》1984,39(1-2):65-90
A theory of the origin and evolution of the Solar System (Alfvén and Arrhenius, 1975, 1976) which considered electromagnetic forces and plasma effects is revised in the light of new information supplied by space research. In situ measurements in the magnetospheres and solar wind have changed our views of basic properties of cosmic plasmas. These results can be extrapolated both outwards in space, to interstellar clouds, and backwards in time, to the formation of the solar system. The first extrapolation leads to a revision of some cloud properties which are essential for the early phases in the formation of stars and solar nebulae. The latter extrapolation makes possible to approach the cosmogonic processes by extrapolation of (rather) well-known magnetospheric phenomena.Pioneer-Voyager observations of the Saturnian rings indicate that essential parts of their structure are fossils from cosmogonic times. By using detailed information from these space missions, it seems possible to reconstruct certain events 4–5 billion years ago with an accuracy of a few percent. This will cause a change in our views of the evolution of the solar system. 相似文献
73.
G. K. Parks C. Gurgiolo C. S. Lin K. A. Anderson R. P. Lin F. Martel H. Réme 《Space Science Reviews》1978,22(6):765-776
This article presents some of the new and important particle features that have been detected in the energy range 1 keV to 290 keV by the ISEE-1 and -2 spacecraft near the magnetopause, bow shock, and the interplanetary space. Only examples of data from the first few orbits, when the spacecraft were on the front side, are shown.Paper presented at 13th ESLAB Symposium, Innsbruck, Austria (June 5, 1978). 相似文献
74.
Theories and Observations of Ion Energization and Outflow in the High Latitude Magnetosphere 总被引:4,自引:0,他引:4
A review is given of several mechanisms causing outflow at high latitudes of ionospheric ions to the terrestrial magnetosphere. The upward ion motion along the geomaagnetic field can be divided into several categories, including polar wind, bulk ion outflow in the auroral region, upwelling ions and ion conics and beams. More than one ion energization mechanism can be operating within each category, and a combination of categories is important for the total ion outflow. 相似文献
75.
J. G. Trotignon J. L. Michau D. Lagoutte M. Chabassière G. Chalumeau F. Colin P. M. E. Décréau J. Geiswiller P. Gille R. Grard T. Hachemi M. Hamelin A. Eriksson H. Laakso J. P. Lebreton C. Mazelle O. Randriamboarison W. Schmidt A. Smit U. Telljohann P. Zamora 《Space Science Reviews》2007,128(1-4):713-728
The main objective of the Mutual Impedance Probe (MIP), part of the Rosetta Plasma Consortium (RPC), is to measure the electron
density and temperature of Comet 67P/Churyumov-Gerasimenko’s coma, in particular inside the contact surface. Furthermore,
MIP will determine the bulk velocity of the ionised outflowing atmosphere, define the spectral distribution of natural plasma
waves, and monitor dust and gas activities around the nucleus. The MIP instrumentation consists of an electronics board for
signal processing in the 7 kHz to 3.5 MHz range and a sensor unit of two receiving and two transmitting electrodes mounted
on a 1-m long bar. In addition, the Langmuir probe of the RPC/LAP instrument that is at about 4 m from the MIP sensor can
be used as a transmitter (in place of the MIP ones) and MIP as a receiver in order to have access to the density and temperature
of plasmas at higher Debye lengths than those for which the MIP is originally designed. 相似文献
76.
77.
Thérèse Encrenaz 《Space Science Reviews》1984,38(1-2):35-87
Our knowledge of the primordial matter from the objects of the outer solar system has made a considerable progress over the past years, in spite of the lack of any in situ measurements of these objects at the present time. The recent progress of ground-based instrumentation and the launch of the two Voyager fly-by missions have provided a huge amount of new informations about the origin and the evolution of the primitive Solar System objects.The most significant discoveries concerning the atmospheres of the Giant Planets can be summarized as follows: (1) there does not seem to be any differentiation in the internal structure of Jupiter during the planet's history; thus, the H2/He ratio measured on Jupiter seems to be representative of the H/He ratio of the Primordial Nebula; (2) there is some evidence for a helium differentiation, relative to hydrogen, in Saturn's interior; (3) there seems to be a carbon enrichment on both Jupiter and Saturn by a factor about 2; this result is consistent with a model in which the planetary core is formed first, and the atmosphere accreted by this core in a second stage; (4) the D/H ratio measured on Jupiter should be representative of the D/H value in the Primordial Nebula, 4.5 billion years ago; this value is 2 to 5 times larger than the mean value measured in the local interstellar medium now; (5) Titan's atmosphere is dominated by nitrogen and contains traces of organic and prebiotic molecules (HCN, C2N2, HC3N); the chemical composition of Titan's atmosphere could be favorable for the early stages of life development.The small bodies of the Solar System — asteroïds and comets — are still very poorly known. However they contain a key information about the physical and chemical properties of dust in the Primordial Nebula and the interstellar medium. With the launch of expected fly-by missions towards Comet Halley and, possibly, towards asteroïds, we may hope to know a new development of our understanding of these objects, comparable to the progress we have known on the Giant Planets over the past ten years. 相似文献
78.
E. Illés A. Horváth 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(8):49-52
L-grooves are the consequence of layered structure of Phobos, which are made up of parallel layers of different composition or hardness. 相似文献
79.
Pierre Léna 《Space Science Reviews》1970,11(1):131-151
Transition between high altitude manned observatories and unmanned balloon-borne or rocket-borne experiments is achieved with high flying aircrafts, at altitudes above tropopause (>12 km), which became readily available, at reasonable cost and reliability, in the past five or ten years.This paper reviews the development of scientific uses of aircrafts, especially for astronomy and geophysics, with some emphasis placed on infrared problems, closely related to the scale height of the chief infrared absorber, i.e. telluric water vapor.Absorbers distribution vs altitude and spectral characteristics are summarized (Figures 1, 2, 3).Capabilities of various available aircrafts are compared (Table I) and the various ways to consider modifications are discussed: structural modifications or design problems to fit telescopes or light collectors on board. Tables II and III list the advantages of airborne observations, compared to other spatial carriers, and also the specific problems connected with aircrafts. Adopted solutions to these problems are exposed (Figures 4, 5, 6, 7) and costs are briefly discussed.Finally, a few examples of scientific results, gathered in the few past years from aircraft, are given, both in astronomy and in geophysics. 相似文献
80.