排序方式: 共有22条查询结果,搜索用时 78 毫秒
1.
2.
Remote sensing and the use of satelites to monitor compliance with arms control and disarmament agreements have been among the focal points of the International Space Year. The interdisciplinary research project, Remote Sensing and European Security, is addressing this question. This article gives a brief survey of the latest developments in the field and summarizes the project's findings. 相似文献
3.
4.
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
5.
Manfred Scholer 《Space Science Reviews》1999,89(1-2):105-114
A brief overview on particle injection and acceleration in corotating interaction regions is presented. After introducing
the diffusion-convection transport equation for energetic particles we discuss diffusive acceleration at the corotating shocks,
stochastic acceleration within the interaction region, and the injection and acceleration of pickup ions at the corotating
shocks.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
F. Dalla Vedova H. Henrion M. Leipold Th. Girot R. Vaudemont Th. Belmonte K. Fleury O. Le Couls 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
SSM (Solar Sail Materials) is an on-going project for the European Space Agency (ESA) relying on past and recent European solar sail design projects. It aims at developing and testing future technologies suitable for large, operational solar sailcrafts. 相似文献
7.
In recent years Micro Systems Technology (MST) was introduced to manufacture miniaturized components for satellite subsystems, like small sensors, valves, micromotors, antennas and many more. These components can be used to build a new class of satellites weighing considerably less than 10 kg, with the capabilities comparable to present microsatellites. With the possibility of cheap mass production of such nanosatellites new applications become possible. However, the construction of very small satellites is connected with problems concerning launch, orbit control and, deorbiting. Furthermore the reduction of size creates certain limits for power consumption, data rates and optical resolutions which have to be carefully considered. 相似文献
8.
9.
Manfred Scholer 《Space Science Reviews》1975,17(1):3-44
Whereas the entry mechanism of energetic solar particles into the open field line region of the magnetosphere is now a rather well understood process, transport processes of solar particles in the closed field line region are still unclear and under dispute. The main difficulty lies not only in the fact that different field models predict different behavior of the particles in the quasi-trapping region (e.g. cut-off latitude), but that dynamic changes of the magnetosphere as geomagnetic storms and substorms greatly influence the particle distribution. The present review tries to summarize the status of knowledge regarding solar proton behavior on closed magnetospheric field lines. Together with a presentation of recent measurements in the closed field line region relevant theoretical problems are discussed. They fall either under the study of single particle motion in different static magnetospheric configurations (due to different field models or due to real, e.g. ring current induced changes), or under the study of resonant interaction processes as pitch angle scattering and radial diffusion.Invited Lecture, Second Meeting of the European Geophysical Society, September 1974, Trieste, Italy. 相似文献
10.
An increasing number of high-resolution spacecraft observations provide access to details of energetic electron and ion velocity-space
distribution structures. Since resonant wave-particle interaction processes depend considerably on the distribution function
details, space plasma modeling is of particular interest for studies of a variety of plasma environments as planetary magnetospheres,
the interplanetary medium or solar flares. After summarizing the most popular particle acceleration processes we focus on
wave-powered energization mechanisms induced by Landau interaction and demonstrate from a time-evolutionary scenario that
power-law distributions, highly favored by observations in recent years, are generated resonantly by an Alfvén wave spectrum
and possibly saturate. This process is further stimulated in non-uniform magnetic field configurations where multiple wave
packets at different phase velocities provide the energy source for a continuous acceleration process. Moreover, in this conjunction
we demonstrate that in particular κ-distributions are a consequence of a generalized entropy concept, favored by nonextensive
statistics, which provides the missing link for power-law plasma models from fundamental physics. With regard to in situ space
observations examples are provided illuminating that for non-thermal plasma characteristics the particular structure of the
velocity-space distribution dominates as regulating mechanism for the wave-particle interaction process over effects related
to changes in space plasma parameters.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献