排序方式: 共有29条查询结果,搜索用时 218 毫秒
1.
Aprajita Verma Vassilis Charmandaris Ulrich Klaas Dieter Lutz Martin Haas 《Space Science Reviews》2005,119(1-4):355-407
Some of the most ‘active’ galaxies in the Universe are obscured by large quantities of dust and emit a substantial fraction
of their bolometric luminosity in the infrared. Observations of these infrared luminous galaxies with the Infrared Space Observatory
(ISO) have provided a relatively unabsorbed view to the sources fuelling this active emission. The improved sensitivity, spatial
resolution and spectroscopic capability of ISO over its predecessor Infrared Astronomical Satellite (IRAS) of enabled significant
advances in the understanding of the infrared properties of active galaxies. ISO surveyed a wide range of active galaxies
which, in the context of this review, includes those powered by intense bursts of star formation as well as those containing
a dominant active galactic nucleus (AGN). Mid-infrared imaging resolved for the first time the dust enshrouded nuclei in many
nearby galaxies, while a new era in infrared spectroscopy was opened by probing a wealth of atomic, ionic and molecular lines
as well as broad band features in the mid- and far-infrared. This was particularly useful, since it resulted in the understanding
of the power production, excitation and fuelling mechanisms in the nuclei of active galaxies including the intriguing but
so far elusive ultraluminous infrared galaxies. Detailed studies of various classes of AGN and quasars greatly improved our
understanding of the unification scenario. Far-infrared imaging and photometry revealed the presence of a new very cold dust
component in galaxies and furthered our knowledge of the far-infrared properties of faint starbursts, ULIGs and quasars. We
summarise almost nine years of key results based on ISO data spanning the full range of luminosity and type of active galaxies. 相似文献
2.
Eberhard Grün Hugo Fechtig Martha S. Hanner Jochen Kissel Bertil-Anders Lindblad Dietmar Linkert Dieter Maas Gregor E. Morfill Herbert A. Zook 《Space Science Reviews》1992,60(1-4):317-340
The Galileo Dust Detector is intended to provide direct observations of dust grains with masses between 10-19 and 10-9 kg in interplanetary space and in the Jovian system, to investigate their physical and dynamical properties as functions of the distances to the Sun, to Jupiter and to its satellites, to study its interaction with the Galilean satellites and the Jovian magnetosphere. Surface phenomena of the satellites (like albedo variations), which might be effects of meteoroid impacts will be compared with the dust environment. Electric charges of particulate matter in the magnetosphere and its consequences will be studied; e.g., the effects of the magnetic field on the trajectories of dust particles and fragmentation of particles due to electrostatic disruption. The investigation is performed with an instrument that measures the mass, speed, flight direction and electric charge of individual dust particles. It is a multicoincidence detector with a mass sensitivity 106 times higher than that of previous in-situ experiments which measured dust in the outer solar system. The instrument weighs 4.2 kg, consumes 2.4 W, and has a normal data transmission rate of 24 bits s-1 in nominal spacecraft tracking mode. On December 29, 1989 the instrument was switched-on. After the instrument had been configured to flight conditions cruise science data collection started immediately. In the period to May 18, 1990 at least 168 dust impacts have been recorded. For 81 of these dust grains masses and impact speeds have been determined. First flux values are given. 相似文献
3.
Jie Jiang Robert H. Cameron Dieter Schmitt Manfred Schüssler 《Space Science Reviews》2013,176(1-4):289-298
To reproduce the weak magnetic field on the polar caps of the Sun observed during the declining phase of cycle 23 poses a challenge to surface flux transport models since this cycle has not been particularly weak. We use a well-calibrated model to evaluate the parameter changes required to obtain simulated polar fields and open flux that are consistent with the observations. We find that the low polar field of cycle 23 could be reproduced by an increase of the meridional flow by 55% in the last cycle. Alternatively, a decrease of the mean tilt angle of sunspot groups by 28% would also lead to a similarly low polar field, but cause a delay of the polar field reversals by 1.5 years in comparison to the observations. 相似文献
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Patrick A. Nsumei Bodo W. Reinisch Xueqin Huang Dieter Bilitza 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The ionospheric characteristics of the F2 layer peak have been measured with ionosondes from the ground or with satellites from space. The most common characteristics are the F2-peak density NmF2 and peak height hmF2. In addition to these two parameters this paper studies the F2-peak scale height. Comparing the median values of hmF2 and NmF2 obtained from topside and bottomside sounding shows good agreement in general. The Chapman scale height values for the F2 layer peak derived from topside profiles, Hm,top, are generally several times larger than Hm,bot derived from bottomside profiles. 相似文献
8.
Yongliang Zhang Larry J. Paxton Dieter Bilitza Rick Doe 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The paper describes the method and initial results of assimilating the auroral peak E-region density (NmE) and the auroral equatorward boundary (EB) into the International Reference Ionosphere (IRI). The NmE and EB are obtained using a FUV based auroral model or FUV measurements in near real-time. Initial results show that the auroral NmE is often significantly larger than the NmE due to the solar EUV. This indicates the importance of including the contribution of precipitating electrons in IRI. The global equatorial boundary helps to improve the specification of the sub-auroral ionosphere trough in IRI. An IDL software package has been developed to interactively display the IRI parameters with assimilated NmE and EB. It can serve as an operational tool for space weather monitoring. 相似文献
9.
Martin Tluczykont Daniel Hampf Dieter Horns Tanja Kneiske Robert Eichler Rayk Nachtigall Gavin Rowell 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The question of the origin of cosmic rays and other questions of astroparticle and particle physics can be addressed with indirect air-shower observations above 10 TeV primary energy. We propose to explore the cosmic ray and γ-ray sky (accelerator sky) in the energy range from 10 TeV to 1 EeV with the new ground-based large-area wide angle (ΔΩ ∼ 0.85 sterad) air-shower detector HiSCORE (Hundred∗i Square-km Cosmic ORigin Explorer). The HiSCORE detector is based on non-imaging air-shower Cherenkov light-front sampling using an array of light-collecting stations. A full detector simulation and basic reconstruction algorithms have been used to assess the performance of HiSCORE. First prototype studies for different hardware components of the detector array have been carried out. The resulting sensitivity of HiSCORE to γ-rays will be comparable to CTA at 50 TeV and will extend the sensitive energy range for γ-rays up to the PeV regime. HiSCORE will also be sensitive to charged cosmic rays between 100 TeV and 1 EeV. 相似文献
10.
Dieter Stöffler 《Space Science Reviews》1991,56(1-2):203-211
The Comet Nucleus Sample Return Mission ROSETTA, a cornerstone mission of ESA jointly planned with NASA, requires the implementation of a highly sophisticated curatorial facility for the returned samples. A concept for the instrumentation and the mode of operation of a Comet Sample Receiving Laboratory (CSRL) is proposed. The main elements of the facility are: (1) cryogenic evacuated cabinets with robotic manipulators, (2) devices for sample dissection, aliquotisation, phase separation, and thin section preparation, and (3) instrumentation for non-destructive chemical and physical analyses and facilities for destructive mineralogical, textural, and (micro)chemical analyses. It is recommended that a very detailed Primary Sample Examination and Analysis be performed on a small representative fraction of the samples at the P-T-conditions of the parent comet nucleus before sample aliquots are released to Principal Investigators. The CSRL should be staffed with top rank personnel and supervised by an international peer review panel which may also be responsible for the selection of investigators and the allocation of samples. 相似文献