共查询到20条相似文献,搜索用时 78 毫秒
1.
O. Witasse T. Cravens M. Mendillo J. Moses A. Kliore A. F. Nagy T. Breus 《Space Science Reviews》2008,139(1-4):235-265
This article reviews our understanding of the ionospheres in the solar system. It provides some basic information on the sources and sinks of the ionospheric plasma, its dynamics, the energetics and the coupling to the neutral atmosphere. Ionospheres in the solar system are reviewed and comparative ionospheric topics are discussed. 相似文献
2.
L. Bengtsson 《Space Science Reviews》2006,125(1-4):187-197
The climate response to changes in radiative forcing depends crucially on climate feedback processes, with the consequence
that solar and greenhouse gas forcing have both similar response patterns in the troposphere. This circumstance complicates
significantly the attribution of the causes of climate change. Additionally, the climate system displays a high level of unforced
intrinsic variability, and significant variations in the climate of many parts of the world are due to internal processes.
Such internal modes contribute significantly to the variability of climate system on various time scales, and thus compete
with external forcing in explaining the origin of past climate extremes. This highlights the need for independent observations
of solar forcing including long-term consistent observational records of the total and spectrally resolved solar irradiance.
The stratospheric response to solar forcing is different from its response to greenhouse gas forcing, thus suggesting that
stratospheric observations could offer the best target for the identification of the specific influence of solar forcing on
climate. 相似文献
3.
Ingrid Mann 《Space Science Reviews》1996,78(1-2):259-264
We discuss present knowledge about interstellar dust grains in the heliosphere in order to give goals for future investigations. As far as the identification of the interstellar flux from brightness observations is concerned we calculate the influence of interstellar dust entering the solar system on the Zodiacal light and Zodiacal emission brightness. In case of the Zodiacal light produced by the scattering of solar radiation, the brightness from interstellar dust within the solar system is not detectable within the limits of present observations. In the case of the thermal emission a distinction of the brightness from the interstellar dust component may be possible. This would be especially interesting for an analysis of the overall spatial distribution of the interstellar flux in the solar system. As far as the identification of the interstellar flux from impact experiments is concerned, parameters like the impact direction are essential. Since the interstellar dust flux is modified in the outer solar system already, it is helpful to probe its variation with increasing distance from the Sun in interstellar upstream direction. 相似文献
4.
Steven R. Cranmer 《Space Science Reviews》2012,172(1-4):145-156
The origins of the hot solar corona and the supersonically expanding solar wind are still the subject of much debate. This paper summarizes some of the essential ingredients of realistic and self-consistent models of solar wind acceleration. It also outlines the major issues in the recent debate over what physical processes dominate the mass, momentum, and energy balance in the accelerating wind. A key obstacle in the way of producing realistic simulations of the Sun-heliosphere system is the lack of a physically motivated way of specifying the coronal heating rate. Recent models that assume the energy comes from Alfvén waves that are partially reflected, and then dissipated by magnetohydrodynamic turbulence, have been found to reproduce many of the observed features of the solar wind. This paper discusses results from these models, including detailed comparisons with measured plasma properties as a function of solar wind speed. Some suggestions are also given for future work that could answer the many remaining questions about coronal heating and solar wind acceleration. 相似文献
5.
The statistical distribution of all available published D/H ratios of carbonaceous chondrites is presented. The possible interpretations
of this distribution are reviewed at the global scale of the solar system planetary objects and at the scale defined by the
carbonaceous meteorites. New issues concerning the chemical origin of the deuterium enrichment in solar system water and organic
molecules are put into light by this exercise. This distribution is a robust constraint on the origin of water on Earth.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Jean-Loup Bertaux Erkki Kyrölä Eric Quemerais Rosine Lallement Walter Schmidt Tuula Summanen Jorge Costa Teemu Mäkinen 《Space Science Reviews》1999,87(1-2):129-132
SWAN is the first space instrument dedicated to the monitoring of the latitude distribution of the solar wind by the Lyman
alpha method. The distribution of interstellar H atoms in the solar system is determined by their destruction during ionization
charge-exchange with solar wind protons. Maps of sky Ly-α emission have been recorded regularly since launch. The upwind maximum
emission region deviates strongly from the pattern that would be expected from a solar wind that is constant with latitude.
It is divided in two lobes by a depression aligned with the solar equatorial plane, called the Lyman-alpha groove, due to
enhanced ionization along the neutral sheet where the slow and dense solar wind is concentrated. The groove (or the anisotropy)
is more pronounced in 1997 than in 1996, but it then decreases between 1997 and 1998.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
G. Rottman 《Space Science Reviews》2006,125(1-4):39-51
The Sun’s electromagnetic radiation powers our solar system. In the case of the Earth it heats the lands and ocean, maintains
our atmosphere, generates clouds, and cycles water. For other planets and minor bodies, similar and appropriate physical processes
occur, also powered by the Sun. The Sun varies on all time scales and a precise knowledge of the Sun's irradiance and its
variation is essential to our understanding of environments and physical conditions throughout our solar system. Measurements
of solar irradiance and its variation can only be made from space, and almost thirty years of observation have now established
that the total solar irradiance (TSI) varies by only 0.1 to 0.3%, while certain portions of the solar spectrum, the ultraviolet
for example, vary by orders of magnitude more. This paper provides an overview of TSI observations and of spectral irradiance
observations from the ultraviolet to the near infrared. 相似文献
8.
The Sun is the largest reservoir of matter in the solar system, which formed 4.6 Gy ago from the protosolar nebula. The solar
wind carries a nearly unfractionated sample of heavy isotopes at energies of about 1 keV/amu from the Sun into interplanetary
space. Data from space missions and theoretical models indicate that the isotopes of the volatile elements N, O, Ne, and Ar
are fractionated by at most a few percent per atomic mass unit in different solar wind regimes. In contrast, isotopic abundances
of solar and heliospheric energetic particles at energies larger than about 100 keV/amu are observed to strongly vary relative
to solar abundances. Processes such as resonant acceleration or pre-acceleration by plasma waves, first-order Fermi acceleration,
or propagation in the interplanetary plasma are discussed as causes for charge-to-mass dependent fractionation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
The voltage-current characteristic of solar cells that provide power for a spacecraft can vary over a wide range. For maximum power transfer from the solar cells to the battery system a power converter has to be designed that adjusts its input impedance to a value equal to the output impedance determined by the operating power characteristic of the solar cells. This paper discusses a circuit and calculations for a design to match this condition. The proposed power converter is simple, lightweight, and reliable and will be used in the Sunblazer satellite. 相似文献
10.
Now extinct short-lived radioactive isotopes were apparently extant in the early solar system. Their abundances can be inferred
from isotopic effects in their daughter nuclei in primitive meteorites, and the deviation of these abundances from expectations
from continuous galactic nucleosynthesis yields important information on the last nucleosynthetic events that contributed
new nuclei to the solar system and on the general circumstances of the Sun's birth. In this paper we present a rudimentary
model that attempts to reconcile the abundances of ten short-lived radioactivities in the early solar system. In broad outlines,
the picture requires 1) that Type Ia supernovae maintained a steady ISM supply of 53Mn and 146Sm, 2) that the r-process events that slowly admixed new 107Pd, 129I, 182Hf, and 244Pu nuclei to the solar system occurred over an interval of several hundred million years prior to solar system formation,
and 3) that a massive star, by injecting only material outside its helium-exhausted core into the proto-solar nebula, contributed
26Al, 36Cl, 41Ca, 60Fe, and 182Hf no more than one million years prior to the Sun's birth. In this picture, the live 182Hf present in the early solar system was not due to r-process production but rather to a fast s-process in helium or carbon
burning shell in the massive star. We conclude with a possible chemical-memory explanation for the putative 53Cr/52Cr gradient in the solar system.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
11.
The discovery of Comet Shoemaker-Levy 9 in March 1993 opened an extraordinary few years in the study of the history of impacts in the solar system. This review paper offers a background that attempts to set the events of 1993 and 1994 into a historical context, and describes events leading to the discovery and the mounting of a unique and unprecedented international effort to observe the comet's collision with Jupiter. A selection of the results is presented to explore how the fate of Comet Shoemaker-Levy 9 has affected scientific and popular understanding of impacts in the solar system. 相似文献
12.
Hyunsu Bae Jaeho Lee Sanghyun Park Bo Cho 《IEEE transactions on aerospace and electronic systems》2008,44(2):538-547
A large-signal stability analysis of the solar array regulator system is performed to facilitate the design and analysis of a low-earth-orbit (LEO) satellite power system. The effective load characteristics of various control methods in the solar array regulator system, such as the constant power load, variable power load, constant voltage load, constant current load, and constant resistive load, are classified to analyze the large-signal stability. Then, using the state plane analysis technique, the large-signal behavior of the solar array system is portrayed and the stability of various equilibrium points is analyzed. Thus, this approach can be contributed to organize the optimal controller structure of the system by representing the relationship between the control method of the solar array regulator and the large-signal stability. For the verification of the proposed large-signal analysis, a solar array regulator system that consists of two 100 W parallel module buck converters has been built and tested using a real 200 W solar array. 相似文献
13.
Herbert Palme 《Space Science Reviews》2000,92(1-2):237-262
The solar system is apparently stratified with regard to the contents of volatile constituents, as judged from the rocky,
volatile-poor inner solar system planets and meteorites and the huge volatile-rich outer planets. However, beyond this gross
structure there is no evidence for a systematic increase of the volatiles' abundances with distance from the Sun. Although
meteorites show comparatively large differences in volatile element contents they also differ in many other respects, such
as Mg/Si-ratios, bulk Fe and refractory element contents. These variations reflect variations in the nebular environment from
which meteorites formed. The various conditions of meteorite formation cannot, however, be related in a simple way to heliocentric
distances.
There are also no systematic variations in the chemistry of the inner planets Mercury, Venus, Earth, Moon, Mars, and including
the fourth largest asteroid Vesta, that could be interpreted as a relationship between volatility and composition. Although
Mars (as judged from the composition of Martian meteorites) is more oxidized and contains more volatile elements than Earth,
this trend cannot be extrapolated to the dry volatile poor Vesta (sampled by HED meteorites) in the asteroid belt. If the
Earth-Mars trend reflects global inner solar system gradients then Vesta must have formed inside Earth's orbit and moved out
later to its present location. The quality of Mercury and Venus composition data is not sufficient to allow reliable extrapolation
to distances closer to the Sun.
Recent nebula models predict small temperature gradients in the inner solar system supporting the view that no large variations
in volatile element contents of inner solar system materials are expected.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
R. Karrer P. Bochsler C. Giammanco F. M. Ipavich J. A. Paquette P. Wurz 《Space Science Reviews》2007,130(1-4):317-321
Using the Mass Time-of-Flight Spectrometer (MTOF)—part of the Charge, Elements, Isotope Analysis System (CELIAS)—onboard the
Solar Heliospheric Observatory (SOHO) spacecraft, we derive the nickel isotopic composition for the isotopes with mass 58,
60 and 62 in the solar wind. In addition we measure the elemental abundance ratio of nickel to iron. We use data accumulated
during ten years of SOHO operation to get sufficiently high counting statistics and compare periods of different solar wind
velocities. We compare our values with the meteoritic ratios, which are believed to be a reliable reference for the solar
system and also for the solar outer convective zone, since neither element is volatile and no isotopic fractionation is expected
in meteorites. Meteoritic isotopic abundances agree with the terrestrial values and can thus be considered to be a reliable
reference for the solar isotopic composition. The measurements show that the solar wind elemental Ni/Fe-ratio and the isotopic
composition of solar wind nickel are consistent with the meteoritic values. This supports the concept that low-FIP elements
are fed without relative fractionation into the solar wind. Our result also confirms the absence of substantial isotopic fractionation
processes for medium and heavy ions acting in the solar wind. 相似文献
15.
Power processing units (PPUs) in an electric propulsion system provide many challenging integration issues. The PPU must provide power to the electric thruster while maintaining compatibility with all of the spacecraft power and data systems. Inefficiencies in the power processor produce heat, which must be radiated to the environment in order to ensure reliable operation. Although PPU efficiencies are generally greater than 0.9, heat loads are often substantial. This heat must be rejected by thermal control systems which generally have specific masses of 15-30 kg/kW. PPUs also represent a large fraction of the electric propulsion system dry mass. Simplification or elimination of power processing in a propulsion system would reduce the electric propulsion system specific mass and improve the overall reliability and performance. A direct drive system would eliminate all or some of the power supplies required to operate a thruster by directly connecting the various thruster loads to the solar array. The development of concentrator solar arrays has enabled power bus voltages in excess of 300 V which is high enough for direct drive applications for Hall thrusters such as the Stationary Plasma Thruster (SPT). The option of solar array direct drive for SPTs is explored to provide a comparison between conventional and direct drive system mass 相似文献
16.
Burnett D.S. Barraclough B.L. Bennett R. Neugebauer M. Oldham L.P. Sasaki C.N. Sevilla D. Smith N. Stansbery E. Sweetnam D. Wiens R.C. 《Space Science Reviews》2003,105(3-4):509-534
The Genesis Discovery mission will return samples of solar matter for analysis of isotopic and elemental compositions in terrestrial
laboratories. This is accomplished by exposing ultra-pure materials to the solar wind at the L1 Lagrangian point and returning
the materials to Earth. Solar wind collection will continue until April 2004 with Earth return in Sept. 2004. The general
science objectives of Genesis are to (1) to obtain solar isotopic abundances to the level of precision required for the interpretation
of planetary science data, (2) to significantly improve knowledge of solar elemental abundances, (3) to measure the composition
of the different solar wind regimes, and (4) to provide a reservoir of solar matter to serve the needs of planetary science
in the 21st century. The Genesis flight system is a sun-pointed spinner, consisting of a spacecraft deck and a sample return
capsule (SRC). The SRC houses a canister which contains the collector materials. The lid of the SRC and a cover to the canister
were opened to begin solar wind collection on November 30, 2001. To obtain samples of O and N ions of higher fluence relative
to background levels in the target materials, an electrostatic mirror (‘concentrator’) is used which focuses the incoming
ions over a diameter of about 20 cm onto a 6 cm diameter set of target materials. Solar wind electron and ion monitors (electrostatic
analyzers) determine the solar wind regime present at the spacecraft and control the deployment of separate arrays of collector
materials to provide the independent regime samples.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
The measured D/H ratios in interstellar environments and in the solar system are reviewed. The two extreme D/H ratios in solar
system water - (720±120)×10−6 in clay minerals and (88±11)×10−6 in chondrules, both from LL3 chondritic meteorites - are interpreted as the result of a progressive isotopic exchange in
the solar nebula between deuterium-rich interstellar water and protosolar H2. According to a turbulent model describing the evolution of the nebula (Drouart et al., 1999), water in the solar system cannot be a product of thermal (neutral) reactions occurring in the solar nebula. Taking
720×10−6 as a face value for the isotopic composition of the interstellar water that predates the formation of the solar nebula, numerical
simulations show that the water D/H ratio decreases via an isotopic exchange with H2. During the course of this process, a D/H gradient was established in the nebula. This gradient was smoothed with time and
the isotopic homogenization of the solar nebula was completed in 106 years, reaching a D/H ratio of 88×10−6. In this model, cometary water should have also suffered a partial isotopic re-equilibration with H2. The isotopic heterogeneity observed in chondrites result from the turbulent mixing of grains, condensed at different epochs
and locations in the solar nebula. Recent isotopic determinations of water ice in cold interstellar clouds are in agreement
with these chondritic data and their interpretation (Texeira et al., 1999).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
《中国航空学报》2023,36(5):125-144
Solar sail technology has been proposed and developed for space explorations with advantages of low launch cost, no-propellant consumption, and continuous thrust, which has great potentials in earth polar detection, interstellar explorations and etc. The development of solar sail has made significant progress in structural design, manufacturing, materials, orbit transfer, and stability control in the past few decades, which makes meaningful contributions to astronomy, physics, and aerospace science. Technological breakthroughs of Solar Radiation Pressure (SRP) propulsion and interstellar transfer have been achieved in current solar sail missions. However, there are still many challenges and problems need to be solved. This paper attempts to summarize the research schemes and potential applications of solar sailing in space missions from the viewpoint of key technologies, so as to provide an overall perspective for researchers in this field. Analyses of the key technologies of solar sailing system design are provided. Finally, challenges and prospective development of solar sailing are discussed. 相似文献
19.
Grasset O. Castillo-Rogez J. Guillot T. Fletcher L. N. Tosi F. 《Space Science Reviews》2017,212(1-2):835-875
Space Science Reviews - Space exploration and ground-based observations have provided outstanding evidence of the diversity and the complexity of the outer solar system. This work presents our... 相似文献
20.
The consequences of the interaction between the solar wind and the local interstellar medium for the wind region enclosed by the heliospheric shock are reviewed. After identifying the principal mechanisms to influence the dynamics of the solar wind, an approach allowing the simultaneous incorporation of neutral atoms, pick-up ions, cosmic rays and energetic electrons into a multifluid model of the expanding wind plasma is outlined. The effects of these particle species are discussed in detail, with special emphasis on the electron component which behaves more like a quasi-static hot gas rather than an expanding fluid. This electron gas is effectively trapped within a three-dimensional trough of a circumsolar electric potential whose outer fringes are possibly determined by the density distribution of anomalous cosmic rays. The electrons are proven to be a globally structered component of great importance for the solar wind momentum flow contributing to a triggering of the solar wind dynamics by asymmetric interstellar boundary conditions. Finally, the consequences for the relative motion of the Sun and the local interstellar medium as well as for the solar system as a whole are described. 相似文献