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91.
Eberhard Haug 《Solar physics》1991,133(1):111-116
During the past decade a number of instruments designed for studying solar oscillations have been developed at the Sayan observatory. A double solar telescope using two Jensch-coelostats and two objective lenses provides the capability to filter lower-order modes. This instrument is also used (in the single-telescope mode) for making observations of the mean magnetic field of the Sun. Spatially-differential methods based on polarization separation of images are best suited for investigations of local oscillations and higher-order modes. These methods make it possible to carry out narrow-band spatial filtering of large wave numbers. They are useful when investigating contrast oscillations as well as the oscillations and rotation of sunspots and other solar features. 相似文献
92.
Eberhard Grün Gregor E. Morfill Richard J. Terrile Torrence V. Johnson Gerhard Schwehm 《Icarus》1983,54(2):227-252
The optical appearance of spokes was studied in high resolution (?200 km/lp) images obtained by Voyager 2. Spokes are classified into three categories. (1) Extended spokes are seen in the distance interval of 100,000 to 112,000 km from Saturn's center. They have diffuse edges and are slightly wedge shaped. Their width at the base (towards Saturn) is about 20,000 km. Their active times (during which they increase in width) range from 4000 to 12,000 sec. (2) Narrow spokes are found in the distance range 104,000 to 116,000 km, have sharply defined edges, and are narrowest at the corotation distance (112, 300 km). Their typical radial extension and width is 6000 and 2,000 km, respectively. (3) Filamentary spokes are found outside 110,000 km mostly joined with a wider spoke further in. They are typically 3000 km in length and 500 km in width. Their active time is less than 1000 sec. Several narrow spokes were observed during formation along radial lines in the sunlit portion of the ring. The formation time is typically ?5 min for a 6000-km-long spoke. The rate of spoke formation is highest at the morning ansa outside Saturn's shadow. Several spokes have been found where one edge revolves with Keplerian speed whereas the other edge stays radial. Recurrent spoke patterns have been observed at the period of Saturn's rotation. From edge-on views of the ring system, an upper limit for the height of spokes of 80 km is derived. 相似文献
93.
X-ray images taken by the Hard X-Ray Imaging Spectrometer (HXIS) aboard SMM during the 1980, November 18 limb flare are analysed. The temporal and spatial evolutions of the X-radiation are described. They differ significantly for hard and soft X-rays. During the elementary flare bursts energetic photons are predominantly emitted from a region close to the solar limb. In contrast, the soft X-ray sources are situated higher in the solar atmosphere. The observed X-ray spectra, in particular those emitted from small source regions at various altitudes, were fitted to power laws. Analysis of the spatial variation of the spectral index shows that there is a systematic tendency of the spectra to get harder with decreasing source altitude, especially during the elementary flare bursts. This fact is in agreement with the existence of nonthermal electron beams precipitating from the corona towards the denser layers of the solar atmosphere. 相似文献
94.
95.
Over its 17 years, the UN's Global Environment Facility (GEF) has allocated US $7.5 billion intended to develop and implement scientifically and socially credible solutions to key global environmental problems such as climate change, biological diversity loss and degradation of transboundary aquatic systems. We studied 906 GEF projects to analyse the challenges that it is facing in delivering solutions that are likely to be sustainable in the long-term. The research included desk reviews of relevant documents and follow-up interviews with a wide range of stakeholders. Some of the challenges the GEF faces are deeply rooted in temporal and spatial mismatches of scale between human economies and their environmental consequences and the strongly sectoral way current society is managed. We conclude that the GEF obtained impressive results for tackling problems of limited complexity and easily quantified benefits but progress is slower on more complex and less tangible problems impeding sustainable development. Potentially, the GEF could enable adaptive management through a ‘learning by doing’ process, transforming it into an innovative mechanism for delivering global benefits. Continued emphasis on ‘easy wins’ would not allow it to achieve this goal. 相似文献
96.
Ralf Srama Thomas Stephan Eberhard Grün Norbert Pailer Anton Kearsley Amara Graps Rene Laufer Pascale Ehrenfreund Nicolas Altobelli Kathrin Altwegg Siegfried Auer Jack Baggaley Mark J. Burchell James Carpenter Luigi Colangeli Francesca Esposito Simon F. Green Hartmut Henkel Mihaly Horanyi Annette Jäckel Sascha Kempf Neil McBride Georg Moragas-Klostermeyer Harald Krüger Pasquale Palumbo Andre Srowig Mario Trieloff Peter Tsou Zoltan Sternovsky Oliver Zeile Hans-Peter Röser 《Experimental Astronomy》2009,23(1):303-328
The scientific community has expressed strong interest to re-fly Stardust-like missions with improved instrumentation. We
propose a new mission concept, SARIM, that collects interstellar and interplanetary dust particles and returns them to Earth.
SARIM is optimised for the collection and discrimination of interstellar dust grains. Improved active dust collectors on-board
allow us to perform in-situ determination of individual dust impacts and their impact location. This will provide important
constraints for subsequent laboratory analysis.
The SARIM spacecraft will be placed at the L2 libration point of the Sun–Earth system, outside the Earth’s debris belts and
inside the solar-wind charging environment. SARIM is three-axes stabilised and collects interstellar grains between July and
October when the relative encounter speeds with interstellar dust grains are lowest (4 to 20 km/s). During a 3-year dust collection
period several hundred interstellar and several thousand interplanetary grains will be collected by a total sensitive area
of 1 m2. At the end of the collection phase seven collector modules are stored and sealed in a MIRKA-type sample return capsule.
SARIM will return the capsule containing the stardust to Earth to allow for an extraction and investigation of interstellar
samples by latest laboratory technologies. 相似文献
97.
Eberhard Grün Ralf Srama Nicolas Altobelli Kathrin Altwegg James Carpenter Luigi Colangeli Karl-Heinz Glassmeier Stefan Helfert Hartmut Henkel Mihaly Horanyi Annette Jäckel Sascha Kempf Markus Landgraf Neil McBride Georg Moragas-Klostermeyer Pasquale Palumbo Han Scholten Andre Srowig Zoltan Sternovsky Xavier Vo 《Experimental Astronomy》2009,23(3):981-999
The DuneXpress observatory will characterize interstellar and interplanetary dust in-situ, in order to provide crucial information
not achievable with remote sensing astronomical methods. Galactic interstellar dust constitutes the solid phase of matter
from which stars and planetary systems form. Interplanetary dust, from comets and asteroids, represents remnant material from
bodies at different stages of early solar system evolution. Thus, studies of interstellar and interplanetary dust with DuneXpress
in Earth orbit will provide a comparison between the composition of the interstellar medium and primitive planetary objects.
Hence DuneXpress will provide insights into the physical conditions during planetary system formation. This comparison of
interstellar and interplanetary dust addresses directly themes of highest priority in astrophysics and solar system science,
which are described in ESA’s Cosmic Vision. The discoveries of interstellar dust in the outer and inner solar system during
the last decade suggest an innovative approach to the characterization of cosmic dust. DuneXpress establishes the next logical
step beyond NASA’s Stardust mission, with four major advancements in cosmic dust research: (1) analysis of the elemental and
isotopic composition of individual interstellar grains passing through the solar system, (2) determination of the size distribution
of interstellar dust at 1 AU from 10 − 14 to 10 − 9 g, (3) characterization of the interstellar dust flow through the planetary system, (4) establish the interrelation of interplanetary
dust with comets and asteroids. Additionally, in supporting the dust science objectives, DuneXpress will characterize dust
charging in the solar wind and in the Earth’s magnetotail. The science payload consists of two dust telescopes of a total
of 0.1 m2 sensitive area, three dust cameras totaling 0.4 m2 sensitive area, and a nano-dust detector. The dust telescopes measure high-resolution mass spectra of both positive and negative
ions released upon impact of dust particles. The dust cameras employ different detection methods and are optimized for (1)
large area impact detection and trajectory analysis of submicron sized and larger dust grains, (2) the determination of physical
properties, such as flux, mass, speed, and electrical charge. A nano-dust detector searches for nanometer-sized dust particles
in interplanetary space. A plasma monitor supports the dust charge measurements, thereby, providing additional information
on the dust particles. About 1,000 grains are expected to be recorded by this payload every year, with 20% of these grains
providing elemental composition. During the mission submicron to micron-sized interstellar grains are expected to be recorded
in statistically significant numbers. DuneXpress will open a new window to dusty universe that will provide unprecedented
information on cosmic dust and on the objects from which it is derived. 相似文献
98.
The Solnhofen Lithographic Limestone and other Upper Jurassic “Solnhofen type” plattenkalks of southeast Germany are famous for pterosaur fossils with soft tissue preservation. Flight membranes, integumentary structures such as pedal scales and bristles as well as pedal webbing are known from these deposits. 相似文献
99.
Stefanie MONNINGER Eberhard FREY Ross ELGIN Helmut TISCHLINGER Julian SARTORI Petra SCHNEIDER 《地球学报》2010,31(Z1):52-52
Preservation of wing membranes in pterosaurs is only reported from a few localities in the world, namely from the Karatau Hills, Kazakhstan (Upper Jurassic), from the Solnhofen Lithographic Limestone, Germany (Upper Jurassic), the Daohugou Beds of China (Upper Jurassic or Lower Cretaceous) and the Crato and Santana Formations, Chapada do Araraipe, NE Brazil (Lower Cretaceous). 相似文献
100.
Daily precipitation forecast of ECMWF verified over Iran 总被引:1,自引:0,他引:1
Sahar Sodoudi Alimohammad Noorian Manfred Geb Eberhard Reimer 《Theoretical and Applied Climatology》2010,99(1-2):39-51
In this paper, the performance of the Centre for Medium Range Weather Forecast (ECMWF) model (t?+?27 h to t?+?51 h) in predicting precipitation is discussed. This model is the first, which has been verified over Iran. The spatial resolution of the model is 0.351° and the 24-h forecasts are compared with daily observations. The study concentrates on year 2001 and the precipitation measurements were collected from the data of 2,048 rain gauges in Iran. The accuracy of four different interpolation methods (nearest neighborhood, inverse distance, kriging, and upscaling) was investigated. Using cross-validation, the inverse distance method (IDM) with minimum mean error was applied. Verification results are given in terms of difference fields (mean error?=?0.46 mm/day), rank–order correlation coefficients (0.70), as well as accuracy scores (false alarm ratio?=?0.50 and probability of detection?=?0.60) and skill scores (true skill statistics [TSS]?=?0.45) in year 2001. The position of the rain band was only partly captured by the ECMWF model; however, the position of maximum precipitations agrees with the observations well. The results show that the high values of TSS are associated with the large amounts of precipitation (over 25 mm). Slight to moderate precipitation events have been underforecasted by the model (bias?<?1) and it leads to a small value of TSS for these thresholds (5–25 mm/day). The ECMWF model has better performance in high and mountainous regions than over flat terrain and in deserts. Comparing TSS over the Alborz and the Zagros Mountains, it is obvious that the ability of the model to predict the convective precipitation events needs some improvement. The amount of daily precipitation has been also slightly overestimated over Iran. From the beginning of January up to 21 March 2001, the ECMWF time series indicates an obvious phase shift of 1 day, although in other months, no phase shift is noticed. 相似文献