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711.
Robert J. Rutten 《Space Science Reviews》1998,85(1-2):269-280
This “rapporteur” report discusses the solar photosphere and low chromosphere in the context of chemical composition studies.
The highly dynamical nature of the photosphere does not seem to jeopardize precise determination of solar abundances in classical
fashion. It is still an open question how the highly dynamical nature of the low chromosphere contributes to first ionization
potential (FIP) fractionation.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
712.
Modulation of cosmic electrons is similar to that of nuclei, but there are clear differences. At energies below 100 MeV the electron spectrum has a negative slope, which may in some way be related to electrons released from the magnetosphere of the planet Jupiter. If there is such a relationship, its nature is not established, and alternative explanations for the upturn exist. At higher energies, electrons are predominantly negatively charged, and it is probable that the difference in net charge sign from that of nuclei is responsible for many of the observed differences in the behavior of electrons and nuclei under modulation. A consistent picture of the cosmic positron abundance and its time variation may be emerging from the world dataset. 相似文献
713.
We study the evolution of artificial granulation on the basis of 2-D hydrodynamical simulations. These clearly show that granules
die in two different ways. One route to death is the well known bifurcation or fragmentation of a large granule into 2 smaller
ones (exploding granules). The other pathway to death is characterized by merging intergranular lanes and the accompanying
dissolution of the granule located between them. It is found that the lifetime and maximum brightness is independent of the
way in which granules evolve and die. They clearly differ in size, however, with exploding granules being in general significantly
larger.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
714.
K. Jelínek Z. Němeček J. Šafránková 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(10):1519-1527
The prediction of the bow shock location is a proof of our understanding of the processes governing the solar wind – magnetosphere interaction. However, the models describing the bow shock location as a function of upstream parameters are based on a statistical processing of bow shock crossings observed by a single spacecraft. Such crossings locate the bow shock in motion, i.e., in a non-equilibrium state and this fact can be a source of significant errors. We have carefully analyzed a long interval of simultaneous observations of the bow shock and magnetopause and another interval of bow shock observations at two well-separated points. Our results suggest that often a small-scale deformation of the bow shock front due to magnetosheath fluctuations is the most appropriate interpretation of observations. Since the low-frequency magnetosheath variations exhibit largest amplitudes, a simultaneous bow shock displacement over a distance of 10–15 RE can be observed. We suggest that bow shock models can be probably improved if the tilt angle would be implemented as a parameter influencing the bow shock location in high latitudes. 相似文献
715.
J. Šafránková Z. Němeček L. Přech A. Koval I. Čermák M. Beránek G. Zastenker N. Shevyrev L. Chesalin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(1):153-159
The monitoring of solar wind parameters is a key problem of the space weather program. We are presenting a new solution of plasma parameter determination suitable for small and fast solar wind monitors. The first version will be launched during the SPECTR-R project into a highly elongated orbit with apogee ∼350,000 km. The method is based on simultaneous measurements of the total ion flux and ion integral energy spectrum by six identical Faraday cups. Three of them are dedicated to determination of the ion flow direction, the other three (equipped with control grids supplied by a retarding potential) are used for determination of the density, temperature, and speed of the plasma flow. The version under development is primarily designed for the measurements in the solar wind and tail magnetosheath, thus for velocities range from 270 to 750 km/s, temperatures from 1 to 30 eV, and densities up to 200 cm−3. However, the instrument design can be simply modified for measurements in other regions with a substantial portion of low-energy plasma as a subsolar magnetosheath, cusp or low-latitude boundary layer. Testing of the engineering model shows that the proposed method can provide reliable plasma parameters with a high time resolution (up to 8 Hz). The paper presents not only the method and its technical realization but it documents all advantages and peculiarities of the suggested approach. 相似文献
716.
J.M. Vaquero M.C. Gallego R.M. Trigo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,40(12):1895-1903
Some periods in the sunspot number reconstruction composed by Hoyt and Schatten [Hoyt, D.V., Schatten, K.H. Group Sunspot Numbers: a new solar activity reconstruction. Sol. Phys. 179, 189–219, 1998. Reprinted with figures in Sol. Phys. 181, 491–512, 1998], are based on very few records. For example, there are only a few solar observations during the years 1736–1739. In this paper we intend to improve the reliability of the sunspot numbers reconstruction developed by Hoyt and Schatten for this 4-years period based on information about solar activity published in three journals of that epoch: “Philosophical Transactions”, “Histoire de l’Académie Royale des Sciences”, and “Nova Acta Eruditorum”. We were able to identify 42 papers with solar observations, including 30 with relevant information on sunspots. Based upon this new outlook, a reconstruction of the monthly solar activity for these years is proposed. 相似文献
717.
R. Jarvinen E. Kallio I. Sillanpää P. Janhunen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(9):1361-1374
This study presents comparisons between the Pioneer Venus Orbiter (PVO) magnetometer (OMAG) observations and the HYB-Venus hybrid simulation code. The comparisons are made near periapsides of four PVO orbits using the full resolution PVO/OMAG data. Also, the statistics of the solar wind and interplanetary magnetic field (IMF) conditions at Venus are studied using the PVO interplanetary dataset. The statistics include the histograms and the probability density maps of the selected upstream parameters. The confidence intervals derived from the upstream statistics demonstrate the nominal simulation input parameter space. Moreover, the probability density maps give the dependencies between the upstream parameters. The comparisons between the simulation code and the data along the spacecraft trajectory show that the basic, large scale, trends seen in the magnetic field can be understood by the current simulation runs. The discrepancies between the simulation and the data were found to arise at low altitudes close to the planetary ionosphere in the region which cannot be resolved in detail by the grid size of the runs. 相似文献
718.
Ulrich Ott 《Space Science Reviews》2007,130(1-4):87-95
Small amounts of pre-solar “stardust” grains have survived in the matrices of primitive meteorites and interplanetary dust
particles. These grains—formed directly in the outflows of or from the ejecta of stars—include thermally and chemically refractory
carbon materials such as diamond, graphite and silicon carbide; as well as refractory oxides and nitrides. Pre-solar silicates,
which have only recently been identified, are the most abundant type except for possibly diamond. The detailed study with
modern analytical tools, of isotopic signatures in particular, provides highly accurate and detailed information with regard
to stellar nucleosynthesis and grain formation in stellar atmospheres. Important stellar sources are Red Giant (RG) and Asymptotic
Giant Branch (AGB) stars, with supernova contributions apparently small. The survival of those grains puts constraints on
conditions they were exposed to in the interstellar medium and in the early solar system. 相似文献
719.
We review results about protoplanetary disk models, protoplanet migration and formation of giant planets with migrating cores.
We first model the protoplanetary nebula as an α–accretion disk and present steady state calculations for different values
of α and gas accretion rate through the disk. We then review the current theories of protoplanet migration in the context
of these models, focusing on the gaseous disk–protoplanet tidal interaction. According to these theories, the migration timescale
may be shorter than the planetary formation timescale. Therefore we investigate planet formation in the context of a migrating
core, considering both the growth of the core and the build–up of the envelope in the course of the migration.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
720.