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21.
T. Dudok de Wit M. Kretzschmar J. Aboudarham P.-O. Amblard F. Auchère J. Lilensten 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The solar EUV irradiance is of key importance for space weather. Most of the time, however, surrogate quantities such as EUV indices have to be used by lack of continuous and spectrally resolved measurements of the irradiance. The ability of such proxies to reproduce the irradiance from different solar atmospheric layers is usually investigated by comparing patterns of temporal correlations. We consider instead a statistical approach. The TIMED/SEE experiment, which has been continuously operating since February 2002, allows for the first time to compare in a statistical manner the EUV spectral irradiance to five EUV proxies: the sunspot number, the f10.7, Ca K, and Mg II indices, and the He I equivalent width. 相似文献
22.
Katia Ferrière 《Space Science Reviews》2006,122(1-4):247-253
We present a theoretical overview of low-frequency waves and instabilities in collisionless, multi-component plasmas with
gyrotropic (
) thermal pressure. We show that the complete dispersion relation can be obtained in the framework of a mixed magnetohydrodynamic
(MHD)-kinetic formalism, which uses the MHD mass, momentum, and induction equations, together with the kinetically corrected
version of the double-adiabatic equations of state. The complete dispersion relation contains not only the three standard
modes (fast, slow, and Alfvén) from double-adiabatic MHD, but also the mirror mode from kinetic theory. We examine the stability
properties of these four modes, firstly in the case of a uniform medium, and secondly in the case of a stratified and rotating
medium. We also discuss the connections with the quasi-interchange modes (interchange and translation) often referred to in
the context of magnetospheric physics. 相似文献
23.
N.V. Jorjio R.A. Kovrazhkin M.M. Mogilevsky J.M. Bosqued H. Rème J.A. Sauvaud C. Béghin J.L. Rauch 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(4):141-144
The plasma diagnostic experiments on the AUREOL-3 satellite have revealed flows of low energy 0+ ions deep inside the night plasmasphere during a large substorm. Flux gradients of the 0+ ions were accompanied by enhancements of ELF electric field noise. The appearance of suprathermal ions at is interpreted within the framework of electrostatic ion-cyclotron acceleration of ionospheric ions in the diffuse auroral zone /12/ followed by a radial displacement of these ions inside the plasmasphere driven by azimuthal electric fields during substorm activity. Electrostatic oscillations observed inside the plasmasphere are apparently associated with gradient instability at the sharp boundaries of suprathermal ion flows. 相似文献
24.
J.M. Bosqued C. Maurel H. Rème J.A. Sauvaud R.A. Kovrazhkin Yu.I. Galperin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(4):135-138
We present a detailed study of the distribution and of the internal structure of the inverted-V electron precipitation commonly detected in the 500 – 2000 km altitude range aboard the AUREOL-3 satellite. These structured precipitations are statistically observed inside the auroral oval with a maximum occurence in the nightside sector. They correspond to primary electron fluxes peaked at energies generally below 10 keV. It is shown that, as predicted by kinetic theories, most inverted-V structures present a clear relationship between the field-aligned current density carried by the 1 – 20 keV primary electrons and the potential drop inferred from particle distribution functions. Furthermore the study demonstrates the existence of strong electron heating, related to the energy gain, when the current density exceeds some threshold of about 1 – 5 μA(m)?2. 相似文献
25.
Geochemistry of Carbonates on Mars: Implications for Climate History and Nature of Aqueous Environments 总被引:1,自引:0,他引:1
Paul B. Niles David C. Catling Gilles Berger Eric Chassefière Bethany L. Ehlmann Joseph R. Michalski Richard Morris Steven W. Ruff Brad Sutter 《Space Science Reviews》2013,174(1-4):301-328
Ongoing research on martian meteorites and a new set of observations of carbonate minerals provided by an unprecedented series of robotic missions to Mars in the past 15 years help define new constraints on the history of martian climate with important crosscutting themes including: the CO2 budget of Mars, the role of Mg-, Fe-rich fluids on Mars, and the interplay between carbonate formation and acidity. Carbonate minerals have now been identified in a wide range of localities on Mars as well as in several martian meteorites. The martian meteorites contain carbonates in low abundances (<1 vol.%) and with a wide range of chemistries. Carbonates have also been identified by remote sensing instruments on orbiting spacecraft in several surface locations as well as in low concentrations (2–5 wt.%) in the martian dust. The Spirit rover also identified an outcrop with 16 to 34 wt.% carbonate material in the Columbia Hills of Gusev Crater that strongly resembled the composition of carbonate found in martian meteorite ALH 84001. Finally, the Phoenix lander identified concentrations of 3–6 wt.% carbonate in the soils of the northern plains. The carbonates discovered to date do not clearly indicate the past presence of a dense Noachian atmosphere, but instead suggest localized hydrothermal aqueous environments with limited water availability that existed primarily in the early to mid-Noachian followed by low levels of carbonate formation from thin films of transient water from the late Noachian to the present. The prevalence of carbonate along with evidence for active carbonate precipitation suggests that a global acidic chemistry is unlikely and a more complex relationship between acidity and carbonate formation is present. 相似文献
26.
Chantal Lathuillère Michel Menvielle 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The performance of JB2008 and NRLMSISE-00 models, in describing the response of the thermosphere to magnetic activity are evaluated against total mass density retrieved from accelerometer measurements made onboard CHAMP satellite during 5 years. We show that the global low- to mid-latitude disturbance amplitude is correctly described by the JB2008 model for low solar activity conditions and by both the JB2008 and the NRLMSISE-00 models for high solar activity conditions. For low solar activity conditions, statistics based on almost 3 years of data confirm the large underestimation by the NRLMSISE-00 model quantified by Lathuillère et al. (2008) for the year 2004. We also found that the time delay between low- to mid-latitude global thermosphere disturbance and magnetic activity is statistically well estimated by the NRLMSISE-00 and JB2008 models for disturbed conditions. For moderately disturbed conditions however, the time delay estimated by the JB2008 model is too large by about 3 h. For very disturbed conditions, we found different time delays during day-time and night-time, using new geomagnetic proxies with a 30-min time resolution. 相似文献
27.
Bethany L. Ehlmann Gilles Berger Nicolas Mangold Joseph R. Michalski David C. Catling Steven W. Ruff Eric Chassefière Paul B. Niles Vincent Chevrier Francois Poulet 《Space Science Reviews》2013,174(1-4):329-364
Clays form on Earth by near-surface weathering, precipitation in water bodies within basins, hydrothermal alteration (volcanic- or impact-induced), diagenesis, metamorphism, and magmatic precipitation. Diverse clay minerals have been detected from orbital investigation of terrains on Mars and are globally distributed, indicating geographically widespread aqueous alteration. Clay assemblages within deep stratigraphic units in the Martian crust include Fe/Mg smectites, chlorites and higher temperature hydrated silicates. Sedimentary clay mineral assemblages include Fe/Mg smectites, kaolinite, and sulfate, carbonate, and chloride salts. Stratigraphic sequences with multiple clay-bearing units have an upper unit with Al-clays and a lower unit with Fe/Mg-clays. The typical restriction of clay minerals to the oldest, Noachian terrains indicates a distinctive set of processes involving water-rock interaction that was prevalent early in Mars history and may have profoundly influenced the evolution of Martian geochemical systems. Current analyses of orbital data have led to the proposition of multiple clay-formation mechanisms, varying in space and time in their relative importance. These include near-surface weathering, formation in ice-dominated near-surface groundwaters, and formation by subsurface hydrothermal fluids. Near-surface, open system formation of clays would lead to fractionation of Mars’ crustal reservoir into an altered crustal reservoir and a sedimentary reservoir, potentially involving changes in the composition of Mars’ atmosphere. In contrast, formation of clays in the subsurface by either aqueous alteration or magmatic cooling would result in comparatively little geochemical fractionation or interaction of Mars’ atmospheric, crustal, and magmatic reservoirs, with the exception of long-term sequestration of water. Formation of clays within ice would have geochemical consequences intermediate between these endmembers. We outline the future analyses of orbital data, in situ measurements acquired within clay-bearing terrains, and analyses of Mars samples that are needed to more fully elucidate the mechanisms of martian clay formation and to determine the consequences for the geochemical evolution of the planet. 相似文献
28.
29.
Dassault Systèmes 《航空制造技术》2012,(19)
Dassault Systèmes作为一家3D体验公司以及在3D设计软件、3D数字化装配和产品生命周期管理(PLM)解决方案领域的全球领导厂商,近期推出了SolidWorks(@)2013,该产品包含新增的和经改进的设计工具,以增强协作、加快模型型创建并简化产品开发流程. 相似文献
30.
H. Balsiger K. Altwegg P. Bochsler P. Eberhardt J. Fischer S. Graf A. Jäckel E. Kopp U. Langer M. Mildner J. Müller T. Riesen M. Rubin S. Scherer P. Wurz S. Wüthrich E. Arijs S. Delanoye J. De Keyser E. Neefs D. Nevejans H. Rème C. Aoustin C. Mazelle J.-L. Médale J. A. Sauvaud J.-J. Berthelier J.-L. Bertaux L. Duvet J.-M. Illiano S. A. Fuselier A. G. Ghielmetti T. Magoncelli E. G. Shelley A. Korth K. Heerlein H. Lauche S. Livi A. Loose U. Mall B. Wilken F. Gliem B. Fiethe T. I. Gombosi B. Block G. R. Carignan L. A. Fisk J. H. Waite D. T. Young H. Wollnik 《Space Science Reviews》2007,128(1-4):745-801
The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) will answer important questions posed by the mission’s
main objectives. After Giotto, this will be the first time the volatile part of a comet will be analyzed in situ. This is
a very important investigation, as comets, in contrast to meteorites, have maintained most of the volatiles of the solar nebula.
To accomplish the very demanding objectives through all the different phases of the comet’s activity, ROSINA has unprecedented
capabilities including very wide mass range (1 to >300 amu), very high mass resolution (m/Δ m > 3000, i.e. the ability to resolve CO from N2 and 13C from 12CH), very wide dynamic range and high sensitivity, as well as the ability to determine cometary gas velocities, and temperature.
ROSINA consists of two mass spectrometers for neutrals and primary ions with complementary capabilities and a pressure sensor.
To ensure that absolute gas densities can be determined, each mass spectrometer carries a reservoir of a calibrated gas mixture
allowing in-flight calibration. Furthermore, identical flight-spares of all three sensors will serve for detailed analysis
of all relevant parameters, in particular the sensitivities for complex organic molecules and their fragmentation patterns
in our electron bombardment ion sources. 相似文献