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31.
C. Fröhlich 《Space Science Reviews》2006,125(1-4):53-65
Since November 1978 a set of total solar irradiance (TSI) measurements from space is available, yielding a time series of
more than 25 years. Presently, there are three TSI composites available, called PMOD, ACRIM and IRMB, which are all constructed
from the same original data, but use different procedures to correct for sensitivity changes. The PMOD composite is the only
one which also corrects the early HF data for degradation. The results from the detailed analysis of the VIRGO radiometry
allow a good understanding of the effects influencing the long-term behaviour of classical radiometers in space. Thus, a re-analysis
of the behaviour of HF/NIMBUS-7 and ACRIM-I/SMM was indicated. For the former the situation is complicated by the fact that
there are no in-flight means to determine changes due to exposure to solar radiation by comparison with a less exposed radiometer
on the same spacecraft. The geometry and optical property of the cavity of HF is, however, very similar to the PMO6-type radiometers,
so the behaviour of the PMO6V radiometers on VIRGO can be used as a model. ACRIM-I had to be revised mainly due to a henceforth
undetected early increase and a more detailed analysis of its degradation. The results are not only important for solar radiometry
from space, but they also provide a more reliable TSI during cycle 21. The differences between the revised PMOD composite
and the ACRIM and IRMB are discussed by comparison with a TSI reconstruction from Kitt-Peak magnetograms. As the PMOD composite
is the only one which has reliable data for cycle 21, the behaviour of the three solar cycles can now be compared and the
similarities and differences discussed. 相似文献
32.
Y. Futaana S. Barabash A. Grigoriev D. Winningham R. Frahm M. Yamauchi R. Lundin 《Space Science Reviews》2006,126(1-4):315-332
As a part of the global plasma environment study of Mars and its response to the solar wind, we have analyzed a peculiar case
of the subsolar energetic neutral atom (ENA) jet observed on June 7, 2004 by the Neutral Particle Detector (NPD) on board
the Mars Express satellite. The “subsolar ENA jet” is generated by the interaction between the solar wind and the Martian
exosphere, and is one of the most intense sources of ENA flux observed in the vicinity of Mars. On June 7, 2004 (orbit 485
of Mars Express), the NPD observed a very intense subsolar ENA jet, which then abruptly decreased within ∼10 sec followed
by quasi-periodic (∼1 min) flux variations. Simultaneously, the plasma sensors detected a solar wind structure, which was
most likely an interplanetary shock surface. The abrupt decrease of the ENA flux and the quasi-periodic flux variations can
be understood in the framework of the global response of the Martian plasma obstacle to the interplanetary shock. The generation
region of the subsolar ENA jet was pushed towards the planet by the interplanetary shock; and therefore, Mars Express went
out of the ENA jet region. Associated global vibrations of the Martian plasma obstacle may have been the cause of the quasi-periodic
flux variations of the ENA flux at the spacecraft location. 相似文献
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基于高度分集的两波束米波雷达测高方法及其应用 总被引:1,自引:0,他引:1
米波雷达的波束较宽、由于地面反射引起波瓣分裂,通常只能估高而不能用来测高.针对这一难题本文提出一种基于高度分集的两波束米波雷达测高方法.该方法采用高度不同的两个天线,利用波瓣分裂情况及相互相位关系来测量目标高度.文章分析了此方法测高的精度及影响精度的一些因素.本测高方法已应用于某型雷达信号处理机中,并取得良好效果. 相似文献
36.
讨论了空射 BTT 导弹的制导命令的生成,特别是针对纵向通道降高问题,设计了一种新的降高段控制指令,然后给出了三个通道的 PID 控制器。六自由度的仿真结果表明这种制导控制设计是成功的。 相似文献
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Recent data and theory for type II solar radio bursts are reviewed, focusing on a recent analytic quantitative theory for
interplanetary type II bursts. The theory addresses electron reflection and acceleration at the type II shock, formation of
electron beams in the foreshock, and generation of Langmuir waves and the type II radiation there. The theory's predictions
as functions of the shock and plasma parameters are summarized and discussed in terms of space weather events. The theory
is consistent with available data, has explanations for radio-loud/quiet coronal mass ejections (CMEs) and why type IIs are
bursty, and can account for empirical correlations between type IIs, CMEs, and interplanetary disturbances.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献