排序方式: 共有13条查询结果,搜索用时 15 毫秒
1.
G. Paschmann M. Boehm H. Höfner R. Frenzel P. Parigger F. Melzner G. Haerendel C. A. Kletzing R. B. Torbert G. Sartori 《Space Science Reviews》1994,70(3-4):447-463
The Electron Beam Instrument (F6) onFreja is the first attempt to apply the electron drift technique in a region of large ambient magnetic fields. The paper describes the operational principles, the technical realization, and the difficulties encountered in the derivation of the electric fields. 相似文献
2.
G. Haerendel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2000,25(12):2379-2388
The paper deals with five selected issues of the dynamical coupling of the near-Earth plasma sheet and magnetosphere, (1) substorm initiation, (2) dipolarization, (3) pressure release of the outer magnetosphere via the auroral energy conversion process, (4) magnetization of the very high beta plasma assembling at the inner edge of the tail, and (5) penetration of energetic particles into the ring current below L 4. One outstanding and strongly debated subject is not discussed here, the origin of the substorm current wedge. The main conclusions (or personal preferences) are: (1) the substorm is initiated by formation of a near-Earth neutral line; (2) dipolarization occurs through magnetic flux transport by the earthward reconnection flow and not by current diffusion; (3) the auroral energy conversion process, the “auroral pressure valve”, contributes substantially to the pressure release during the substorms; (4) high beta ( 10) plasma breaks up into smaller scale blobs under slow magnetization; and (5) deep and prolonged penetration of hot plasma sheet plasma into the middle magnetosphere produces currents and electric fields which lead to the growth of the storm-time ring current. 相似文献
3.
4.
Gerhard Haerendel 《Space Science Reviews》2006,124(1-4):317-331
Three types of processes, occurring in the weakly ionized plasmas of the Earth’s ionosphere as well as in the solar chromosphere,
are being compared with each other. The main objective is to elaborate on the differences introduced primarily by the grossly
different magnitudes of the densities, both with respect to the neutral and, even more so, to the plasma constituents. This
leads to great differences in the momentum coupling from the plasma to the neutral component and becomes clear when considering
the direct electric current component transverse to the magnetic field, called “Pedersen current”; in the ionosphere, which
has no quasi-static counterpart in the chromosphere. The three classes of processes are related to the dynamical response
of the two plasmas to energy influx from below and from above. In the first two cases, the energy is carried by waves. The
third class concerns plasma erosion or ablation in the two respective regions in reaction to the injection of high Poynting
and/or energetic particle fluxes. 相似文献
5.
Gerda Horneck Angioletta Coradini Gerhard Haerendel May-Britt Kallenrode Paul Kamoun Jean Pierre Swings Alberto Tobias Jean-Jacques Tortora 《Space Policy》2010
As a result of increasing public and political interest in ‘space’ (i.e. solar system) exploration at the global scale, the Space Advisory Group of the European Commission has evaluated the situation in Europe with regard to its potential to participate in this ambitious global enterprise. Aspects of science, technology, environment and safety, society, spin-offs and international cooperation were all considered. The group concluded that Europe possesses sufficient key technologies and scientific expertise to play a major role in international space exploration and has recommended that the EU take a central role to ensure the success of future European space exploration, not only to give a clear political signal for the way forward but also to ensure an appropriate financial framework. In this way Europe would embrace the spirit of the European Space Policy and contribute to the knowledge-based society by investing significantly in space-based science and technology, thereby playing a strong role in international space exploration. 相似文献
6.
Freja
*, a joint Swedish and German scientific satellite launched on october 6 1992, is designed to give high temporal/spatial resolution measurements of auroral plasma characteristics. A high telemetry rate (520 kbits s–1) and 15 Mbyte distributed on board memories that give on the average 2 Mbits s–1 for one minute enablesFreja to resolve meso and micro scale phenomena in the 100 m range for particles and 1–10 m range for electric and magnetic fields. The on-board UV imager resolve auroral structures of kilometer size with a time resolution of one image per 6 s. Novel plasma instruments giveFreja the capability to increase the spatial/temporal resolution orders of magnitudes above that achieved on satellites before. The scientific objective ofFreja is to study the interaction between the hot magnetospheric plasma with the topside atmosphere/ionosphere. This interaction leads to a strong energization of magnetospheric and ionospheric plasma and an associated erosion, and loss, of matter from the Terrestrial exosphere.Freja orbits with an altitude of 600–1750 km, thus covering the lower part of the auroral acceleration region. This altitude range hosts processes that heat and energize the ionospheric plasma above the auroral zone, leading to the escape of ionospheric plasma and the formation of large density cavities. 相似文献
7.
G. Haerendel R.Z. Sagdeev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(2):29-46
The PORCUPINE sounding rocket project provided the opportunity to study the dynamics of an artificially injected plasma beam in the near-Earth space. The structure of the plasma beam, its propagation across the magnetic field as well as the resulting wave phenomena will be discussed. 相似文献
8.
G. Paschmann F. Melzner R. Frenzel H. Vaith P. Parigger U. Pagel O. H. Bauer G. Haerendel W. Baumjohann N. Scopke R. B. Torbert B. Briggs J. Chan K. Lynch K. Morey J. M. Quinn D. Simpson C. Young C. E. Mcilwain W. Fillius S. S. Kerr R. Mahieu E. C. Whipple 《Space Science Reviews》1997,79(1-2):233-269
The Electron Drift Instrument (EDI) measures the drift of a weak beam of test electrons that, when emitted in certain directions, return to the spacecraft after one or more gyrations. This drift is related to the electric field and the gradient in the magnetic field, and these quantities can, by use of different electron energies, be determined separately. As a by-product, the magnetic field strength is also measured. The present paper describes the scientific objectives, the experimental method, and the technical realization of the various elements of the instrument. 相似文献
9.
J. Kissel K. Altwegg B. C. Clark L. Colangeli H. Cottin S. Czempiel J. Eibl C. Engrand H. M. Fehringer B. Feuerbacher M. Fomenkova A. Glasmachers J. M. Greenberg E. Grün G. Haerendel H. Henkel M. Hilchenbach H. von Hoerner H. Höfner K. Hornung E. K. Jessberger A. Koch H. Krüger Y. Langevin P. Parigger F. Raulin F. Rüdenauer J. Rynö E. R. Schmid R. Schulz J. Silén W. Steiger T. Stephan L. Thirkell R. Thomas K. Torkar N. G. Utterback K. Varmuza K. P. Wanczek W. Werther H. Zscheeg 《Space Science Reviews》2007,128(1-4):823-867
The ESA mission Rosetta, launched on March 2nd, 2004, carries an instrument suite to the comet 67P/Churyumov-Gerasimenko. The COmetary Secondary Ion Mass Anaylzer – COSIMA – is one of three cometary dust analyzing instruments onboard Rosetta. COSIMA is based on the analytic measurement method of secondary ion mass spectrometry (SIMS). The experiment’s goal is in-situ analysis of the elemental composition (and isotopic composition of key elements) of cometary grains. The chemical characterization will include the main organic components, present homologous and functional groups, as well as the mineralogical and petrographical classification of the inorganic phases. All this analysis is closely related to the chemistry and history of the early solar system. COSIMA covers a mass range from 1 to 3500 amu with a mass resolution m/Δm @ 50% of 2000 at mass 100 amu. Cometary dust is collected on special, metal covered, targets, which are handled by a target manipulation unit. Once exposed to the cometary dust environment, the collected dust grains are located on the target by a microscopic camera. A pulsed primary indium ion beam (among other entities) releases secondary ions from the dust grains. These ions, either positive or negative, are selected and accelerated by electrical fields and travel a well-defined distance through a drift tube and an ion reflector. A microsphere plate with dedicated amplifier is used to detect the ions. The arrival times of the ions are digitized, and the mass spectra of the secondary ions are calculated from these time-of-flight spectra. Through the instrument commissioning, COSIMA took the very first SIMS spectra of the targets in space. COSIMA will be the first instrument applying the SIMS technique in-situ to cometary grain analysis as Rosetta approaches the comet 67P/Churyumov-Gerasimenko, after a long journey of 10 years, in 2014. 相似文献
10.
M. Boehm G. Paschmann J. Clemmons H. Höfner R. Frenzel M. Ertl G. Haerendel P. Hill H. Lauche L. Eliasson R. Lundin 《Space Science Reviews》1994,70(3-4):509-540
The two-dimensional electron spectrometer onFreja consists of a top-hat-type electrostatic analyzer with the addition of entrance aperture deflection plates. The field of view of the concentric-hemisphere analyzer is modified from a plane to a cone up to 25° from this plane by application of bipolar high voltages to the deflection plates. Fast high-voltage sweeps allow full 10 eV–25 KeV, 500-point distribution function measurements in 32 ms. Constant-energy or limited energy-sweep modes allow time resolutions down to 1 ms.A set of electronics combines the electron data with F4 wave data to allow on-board calculations of cross-correlations between electron fluxes and wave electric fields. Additionally, a fast signal processor is capable of searching the electron pulse sequence from one or several channeltrons for high-frequency modulations in the electron flux. 相似文献