排序方式: 共有76条查询结果,搜索用时 46 毫秒
31.
32.
33.
T. Flohrer T. SchildknechtR. Musci 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(7):1010-1021
Two ESA-funded feasibility studies that aimed to develop observation strategies, to propose suitable sensor architectures, and to assess the expected performance of an independent European Space Surveillance System were carried out during the last years. The French company ONERA led two study teams comprising a number of European companies. 相似文献
34.
X.-Y. Zhou D. Lummerzheim G.R. Gladstone S.D. Gunapala S.B. Bandara J. Trihne L. Herrell 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
Daylight auroral imaging is a proposed application of the NASA high-altitude long-duration balloon technology. This paper discusses the theoretical background of this application and test observations, for proof of the feasibility. It is demonstrated that nitrogen auroral emissions in the near-infrared band are detectable at altitudes of 35–40 km and above using a near-infrared InGaAs camera. The purpose of such observations is to identify auroral small-scale structures that are manifestations of auroral particle accelerations and the solar wind – magnetosphere – ionosphere interaction. Use of this new approach will enable studies of the dayside aurora, low-latitude aurora, and storm-time and substorm-time auroral conjugacy. 相似文献
35.
Giuseppe Nisticò Spiros Patsourakos Volker Bothmer Gaetano Zimbardo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Coronal hole jets are fast ejections of plasma occurring within coronal holes, observed at Extreme-UltraViolet (EUV) and X-ray wavelengths. Recent observations of jets by the STEREO and Hinode missions show that they are transient phenomena which occur at much higher rates than large-scale impulsive phenomena like flares and Coronal Mass Ejections (CMEs). In this paper we describe some typical characteristics of coronal jets observed by the SECCHI instruments of STEREO spacecraft. We show an example of 3D reconstruction of the helical structure for a south pole jet, and present how the angular distribution of the jet position angles changes from the Extreme-UltraViolet-Imager (EUVI) field of view to the CORonagraph1 (COR1) (height ∼2.0 R⊙ heliocentric distance) field of view. Then we discuss a preliminary temperature determination for the jet plasma by using the filter ratio method at 171 and 195 Å and applying a technique for subtracting the EUV background radiation. The results show that jets are characterized by electron temperatures ranging between 0.8 and 1.3 MK. We present the thermal structure of the jet as temperature maps and we describe its thermal evolution. 相似文献
36.
This paper contains a summary of the topics treated in the working group on abundance variations in the solar atmosphere and
in the solar wind. The FIP bias (overabundance of particles with low First Ionization Potentials over photospheric abundances)
in coronal holes and coronal hole associated solar wind amounts to values between 1 and 2. The FIP bias in the slow solar
wind is typically a factor 4, consistent with optical observations in streamers. In order to distinguish between different
theoretical models which make an attempt to explain the FIP bias, some observable parameters must be provided. Unfortunately,
many models are deficient in this respect. In addition to FIP fractionation, gravitational settling of heavy elements has
been found in the core of long lived streamers. The so-called electron 'freeze in' temperatures derived from in situ observed
ionization states of minor ions in the fast wind are significantly higher than the electron temperatures derived from diagnostic
line ratios observed in polar coronal holes. The distinction between conditions in plumes and interplume lanes needs to be
further investigated. The 'freeze in' temperatures for the slow solar wind are consistent with the electron temperatures derived
for streamers.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
37.
The Processing of Band-Limited Measurements; Filtering Techniques in the Least Squares Context and in the Presence of Data Gaps 总被引:2,自引:0,他引:2
This paper discusses the treatment of correlated measurements in the least squares context. We focus on the processing of
band-limited measurements and on long time series with a constant sampling interval. Time domain as well as frequency domain
approaches were discussed to offer different ways to integrate the filtering process into the optimization scheme as good
as possible. The focus was on long equispaced data sets. The application of discrete filters in the space domain makes it
possible to decorrelate the observations during data acquisition. This opens the way to a sequential adjustment procedure,
where the design matrix is treated row-by-row. Huge systems with millions of observations can be solved by direct or iterative
strategies, and both approaches benefit from well-tailored filter techniques. Because of the sequential access the computational
effort of this giant task can be easily distributed to a cluster of parallel processors and offers, in addition, the possibility
to treat data gaps in a straightforward way.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
38.
Florencia L. Vieyro Gustavo E. Romero 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
We present a model for neutrino flares in accreting black holes based on the injection of a non-thermal population of relativistic particles in a magnetized corona. The most important products of hadronic and photohadronic interactions at high energies are pions. Charged pions decay into muons and neutrinos; muons also decay yielding neutrinos. Taking into account these effects, coupled transport equations are solved for all species of particles and the neutrino production is estimated for the case of accreting galactic black holes. 相似文献
39.
G. J. Molina-Cuberos J. Porti B. P. Besser J. A. Morente J. Margineda H. I. M. Lichtenegger A. Salinas K. Schwingenschuh H. U. Eichelberger 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,33(12):2309-2313
Among the multiple questions that the CASSINI/HUYGENS mission tries to answer is the likelihood of electric discharges in Titan's atmosphere. The instruments “Huygens Atmospheric Structure Instrument” and “Radio and Plasma Wave Science” will probe the electromagnetic emissions during the Huygens descent and Cassini flybys, respectively. Although no lightning was observed during Voyager's encounters with Titan in 1980 and 1981, this does not exclude the existence of lightning phenomena. Recent investigations show that lightning discharges could occur in the lower atmosphere, such as the detection of methane condensation clouds in the troposphere and the theoretical prediction of an electric field that would be sufficient enough to cause lightning. We present a numerical model of Titan's atmosphere with the aim of calculating the resonance frequencies and the atmospheric transparency to electromagnetic waves. The detection and measurement of these resonances, Schumann frequencies, by the Huygens probe, would show the existence of electric activity connected with lightning discharges in the atmosphere. As it happens with the Schumann frequencies of Earth, losses associated with the electric conductivity will make these frequencies to be lower than the theoretically predicted, the fundamental one being located between 11 and 15 Hz. An analytical study shows that the strong losses associated with the high conductivity make it impossible that an electromagnetic wave generated near the surface with a frequency of 10 MHz or lower reaches the outer part of Titan's atmosphere. Therefore the detection of electromagnetic waves coming from Titan's lower atmosphere by the RPWS instrument is very unlikely. 相似文献
40.
Floris van der Tak 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
This paper contains a summary of the results from the first years of observations with the HIFI instrument onboard ESA’s Herschel space observatory. The paper starts by outlining the goals and possibilities of far-infrared and submillimeter astronomy, the limitations of the Earth’s atmosphere, and the scientific scope of the Herschel-HIFI mission. The presentation of science results from the mission follows the life cycle of gas in galaxies as grouped into five themes: Structure of the interstellar medium, First steps in interstellar chemistry, Formation of stars and planets, Solar system results and Evolved stellar envelopes. The HIFI observations paint a picture where the interstellar medium in galaxies has a mixed, rather than a layered structure; the same conclusion may hold for protoplanetary disks. In addition, the HIFI data show that exchange of matter between comets and asteroids with planets and moons plays a large role. The paper concludes with an outlook to future instrumentation in the far-infrared and submillimeter wavelength ranges. 相似文献