Stokes profiles inversion techniques

Inversion techniques of the radiative transfer equation for polarized light are presented as one of the best current procedures to infer the vector magnetic field, as well as other quantities governing the physical state of the atmospheric layers that photons are coming from. Several characteristics of the various available inversion procedures are pointed out. They are mostly based on the diagnostic contents of the spectral lines as well as on the main hypotheses assumed in these procedures. In particular, the role of gradients in the atmospheric quantities is emphasized as of paramount importance in any diagnostic analysis and, hence, in any interpretation of inversion results.     

BPL脉位调制方案及数据传送

实现BPL长波信道能力扩展的一个重要技术环节是对组重复间隔（GRI）脉冲的脉位调制,在将信源消息变成脉位调制电平的数据传输过程中,还有一系列的信号格式转换,提出了实现脉位调制的若干方法,探讨了数据流的详细传送过程并给出了相应的软件。     

Rotational perturbations of radiating Universes coupled with zero-mass scalar field

Investigations are made on slowly rotating radiating Universes coupled with a scalar field in the spherically symmetric Einstein formalism, and some new interesting solutions are obtained. Their physical and geometrical properties are studied from various angles. The rotational perturbations of such models are examined in order to substantiate the possibility that the universe is endowed with some rotation. The nature and role of the metric rotation as well as that of the rotation of matter are studied, and the effects of radiation and scalar fields on them are discussed. The models here turn out to be rotating as well as expanding ones, which may be taken as good examples of real astrophysical objects in this universe. The periods of the physical validity and the restrictions on the radii of the models for real astrophysical situations are obtained and discussed. The models obtained here are theoretically satisfactory and therefore there is a possibility that there may be less known objects in this universe which may be represented by our model Universes obtained here and many unknown properties of this universe may be explored and unfolded in the study of these models.     

Rotational perturbations of charged cosmological viscous-fluid universes coupled with a scalar field

The dynamics of a slowly rotating charged viscous-fluid Universe coupled with a zero-mass scalar field is investigated; and the rotational perturbations of such models are studied in order to substantiate the possibility that the Universe is endowed with slow rotation, in the course of presentation of several new analytic solutions. The effects of charged field and scalar field on the rotational motion are discussed. Except for perfect dragging, the scalar field as well as the charged field is found to have a damping effect on the rotation of matter. Rotating models which are expanding as well are obtained, in which cases the rotational velocities are found to decay with the time, and these models may be taken as good examples of real astrophysical situations. The periods of physical validity of different models are also obtained.     

On Pfaff's equations of motion in dynamics; Applications to satellite theory

In this article we study a form of equations of motion which is different from Lagrange's and Hamilton's equations: Pfaff's equations of motion. Pfaff's equations of motion were published in 1815 and are remarkably elegant as well as general, but still they are much less well known. Pfaff's equations can also be considered as the Euler-Lagrange equations derived from the linear Lagrangian rather than the usual Lagrangian which is quadratic in the velocity components. The article first treats the theory of changes of variables in Pfaff's equations and the connections with canonical equations as well as canonical transformations. Then the applications to the perturbed two-body problem are treated in detail. Finally, the Pfaffians are given in Hill variables and Scheifele variables. With these two sets of variables, the use of the true anomaly as independent variable is also considered.     

Limits to the accuracy of the 10.7 cm flux

The 10.7 cm flux data, which are widely used as an index of solar activity, are actually spot measurements of the solar flux density at 10.7 cm wavelength, made three times each day, usually at 17:00, 20:00, and 23:00 UT. These values, or the 20:00 UT determination alone, are frequently used as the average flux for that day. Since each spot measurement takes about one hour to make, and the Sun's emissions at that wavelength can vary over time scales shorter than the intervals between the measurements, the data are unavoidably undersampled. Radio emissions from transient events, such as flares, are defined as contaminants of the flux, and largely-empirical procedures have evolved which are used to filter them from the data. The utility of theF _10.7 index over more than 40 years suggests that the consequences of the under-sampling and the use of largely-empirical data filters are not serious. However, as new applications of the flux data appear, and existing ones become more quantitative, we need to better understand the accuracy of data as estimates of the 10.7 cm flux index, and to know how much precision we can reasonably expect to attain. In this paper we describe part of a study aimed at estimating how good the spot measurements are as estimators of the ‘daily-average’ flux. By a combination of measurement and modelling, the contributions to the flux monitor output truly due to the Sun are separated from the non-solar signals. We then derive the daily average 10.7 cm flux values and compare them with the spot measurements. We find that in general, the spot measurements are usually within a percent or so of the daily-average fluxes.     

Hidden subluminous stars among the FAUST UV sources towards Ophiuchus

We present results of an analysis of a UV image in the direction of Ophiuchus, obtained with the FAUST instrument. The image contains 228 UV sources. Most of these are identified as normal early-type stars through correlations with catalogued objects. For the first time in this project we identify UV sources as such stars by selecting suitable candidates in crowded fields as the bluest objects in colour–colour diagrams using observations from the Wise Observatory. These candidates are then studied using low-resolution spectroscopy, which allows the determination of spectral types to an accuracy of about one-half class, for 60 stars.
Synthetic photometry of spectral data is performed in order to predict the expected UV emission, on the basis of the photometric information. These results are used along with the Hipparcos /Tycho information, to search for subluminous stars. The comparison of the predicted emission with the FAUST measured magnitudes allows us to select 12 stars as highly probable evolved hot stars. High signal-to-noise spectra are obtained for nine of these stars, and Balmer line profiles are compared with the prediction of atmosphere models and with the spectrum of real stellar atmospheres. Among the nine candidates, six are classified as previously unrecognized sdB stars, and two as white dwarfs. Our result indicates that indeed more bright subluminous stars are still unrecognized in the existing samples.     

Taxonomy of asteroids

A taxonomic system was introduced by C. R. Chapman, D. Morrison, and B. Zellner [Icarus25, 104–130 (1975)], in which minor planets are classified according to a few readily observable optical properties, independent of specific mineralogical interpretations. That taxonomy is here augmented to five classes, now precisely defined in terms of seven parameters obtained from polarimetry, spectrophotometry, radiometry, and UBV photometry of 523 objects. We classify 190 asteroids as type C, 141 as type S, 13 as type M, 3 as type E, and 3 as type R; 55 objects are shown to fall outside these five classes and are designated U (unclassifiable). For the remaining 118, the data exclude two or more types but are insufficient for unambiguous classification. Reliable diameters, from radiometry or polarimetry or else from albedos adopted as typical of the types, are listed for 396 objects. We also compare our taxonomy with other ones and discuss how classification efforts are related to the interpretation of asteroid mineralogies.     

Alfvén-Jeans and Magnetosonic Modes in Multispecies Self-Gravitating Dusty Plasmas

Perpendicularly propagating electromagnetic waves in magnetized, multispecies, self-gravitating dusty plasmas are investigated in terms of their wave dispersion properties as well as with respect to their susceptibility to gravitational collapse. In particular, waves on the ordinary as well as extraordinary mode branches are considered. Within the one-dimensional propagation model employed, all modes except the ordinary mode produce density perturbations that can be unstable to gravitational collapse. The wavelengths that are unstable are comparable to the well-known Jeans length for a neutral gas/dust, but there are interesting modifications due to the presence of a magnetic field and charged particles. Furthermore, the effects of the gravitational coupling of a multicomponent plasma to a neutral dust are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Approximate analysis for relative motion of satellite formation flying in elliptical orbits

This paper studies the relative motion of satellite formation flying in arbitrary elliptical orbits with no perturbation. The trajectories of the leader and follower satellites are projected onto the celestial sphere. These two projections and celestial equator intersect each other to form a spherical triangle, in which the vertex angles and arc-distances are used to describe the relative motion equations. This method is entitled the reference orbital element approach. Here the dimensionless distance is defined as the ratio of the maximal distance between the leader and follower satellites to the semi-major axis of the leader satellite. In close formations, this dimensionless distance, as well as some vertex angles and arc-distances of this spherical triangle, and the orbital element differences are small quantities. A series of order-of-magnitude analyses about these quantities are conducted. Consequently, the relative motion equations are approximated by expansions truncated to the second order, i.e. square of the dimensionless distance. In order to study the problem of periodicity of relative motion, the semi-major axis of the follower is expanded as Taylor series around that of the leader, by regarding relative position and velocity as small quantities. Using this expansion, it is proved that the periodicity condition derived from Lawden’s equations is equivalent to the condition that the Taylor series of order one is zero. The first-order relative motion equations, simplified from the second-order ones, possess the same forms as the periodic solutions of Lawden’s equations. It is presented that the latter are further first-order approximations to the former; and moreover, compared with the latter more suitable to research spacecraft rendezvous and docking, the former are more suitable to research relative orbit configurations. The first-order relative motion equations are expanded as trigonometric series with eccentric anomaly as the angle variable. Except the terms of order one, the trigonometric series’ amplitudes are geometric series, and corresponding phases are constant both in the radial and in-track directions. When the trajectory of the in-plane relative motion is similar to an ellipse, a method to seek this ellipse is presented. The advantage of this method is shown by an example.     

Solar rotation and the giant cells

Departures from the mean solar differential rotation rate as a function of latitude, longitude, and epoch of the solar cycle, together with variations in the rotation rate as determined by spectroscopic and tracer measurements are reviewed. It is shown that, if giant convection cells do exist as predicted, real variations in the subsurface rotation rate should occur and that this may be responsible for the observed surface anomalies.In terms of this hypothesis, a simple account is given for the anomalous rotation rates of sunspots. Furthermore, the torsional oscillations are identified as a modulation of the differential rotation produced by a system of toroidal convective rolls generated near the poles and propagating towards the equator. It is suggested that, as these rolls progress through lower latitudes, they break up into a system of cells which are the long sought for giant cells of the convection zone. Thus the torsional oscillations are identified as direct surface evidence for the existence of these cells.Solar Cycle Workshop Paper.     

Narrowing effects on lines by strong correlation between highly excited states (I)

Overlapping recombination line parameters are searched. The dynamical equations are formulated, and the limits of their acceptance are discussed in detail. Except formal solutions for characteristic functions or lines profiles, relations for lines displacement are both represented with narrowed effective width.Particle impact scattering, as well as the strong influence of quasistationary plasma fields are accounted for. Effects of highly excited states interference due to powerful electromagnetic waves interaction are also studied. Some of the asymptotics found are compared with well-known ones.In optically thick media, associated with lines narrowing conditions, recombination lines conserve the energy of quanta in the limits of line width effectively enough to make them visible, e.g. as for decametric lines of ions.     

Head-on collision between positron acoustic waves in homogeneous and inhomogeneous plasmas

The head-on collision between positron acoustic solitary waves (PASWs) as well as the production of rogue waves (RWs) in homogeneous and PASWs in inhomogeneous unmagnetized plasma systems are investigated deriving the nonlinear evolution equations. The plasmas are composed of immobile positive ions, mobile cold and hot positrons, and hot electrons, where the hot positrons and hot electrons are assumed to follow the Kappa distributions. The evolution equations are derived using the appropriate coordinate transformation and the reductive perturbation technique. The effects of concentrations, kappa parameters of hot electrons and positrons, and temperature ratios on the characteristics of PASWs and RWs are examined. It is found that the kappa parameters and temperature ratios significantly modify phase shifts after head-on collisions and RWs in homogeneous as well as PASWs in inhomogeneous plasmas. The amplitudes of the PASWs in inhomogeneous plasmas are diminished with increasing kappa parameters, concentration and temperature ratios. Further, the amplitudes of RWs are reduced with increasing charged particles concentration, while it enhances with increasing kappa- and temperature parameters. Besides, the compressive and rarefactive solitons are produced at critical densities from KdV equation for hot and cold positrons, while the compressive solitons are only produced from mKdV equation for both in homogeneous and inhomogeneous plasmas.     

The Key Techniques and Design Features of YH-1 Mars Probe

In this paper, the function and composition as well as the key techniques (ultra-long distance communication, attitude determination and control, thermal control, ultra-low temperature acclimatization, etc.) of China's first Mars probe are analyzed. In combination with practical engineering conditions, the solutions of these key techniques are given. The design features of the probe are summarized, as a reference for developing the probes of the subsequent related missions in China.     

对地日冕物质抛射研究

日冕物质抛射，作为太阳大气中频繁发生的极为壮观的活动现象，越来越受到太阳物理学家的关注。其中一类特殊的抛射事件－－对地日冕物质抛射，通常与大的地磁暴、行星际激波和高能粒子事件相伴生，具有强烈的地球物理效应，是影响空间天气的主要因素之一。概括了对地日冕物质抛射的研究现状，重点介绍了与对土日冕物质抛射事件相联系的光球向量磁场演化的观测研究成果，并由典型事件探讨了暗条爆发、耀五等剧烈太阳活动和对地日冕物质抛射之间的密切关系，提出了尚待解决的主要问题和进一步的研究方向。     

Parametric instabilities and nucleation of coupled Langmuir and acoustic waves in a weakly-ionized plasma

A pair of coupled equations governing the nonlinear interaction between Langmuir and acoustic waves in partially-ionized plasmas are presented. Three-wave decay interactions, modulatinal instabilities, as well as the nucleation of coupled Langmuir and acoustic waves can then be studied. The results are of relevance to the lower part of the ionosphere, radio-frequency driven gas discharges, as well as the interstellar medium.     

Observational Evidence of Dissipative Small Scale Processes: Geotail Spacecraft Observation and Simulation of Electrostatic Solitary Waves

In recent spacecraft observations, coherent microscale structures such as electrostatic solitary waves are observed in various regions of the magnetosphere. The Geotail spacecraft observation has shown that these solitary waves are associated with high energy non-thermal electrons flowing along the magnetic field. The solitary structures are generated as a result of a long time evolution of coherent nonlinear trapping of electrons as found in bump-on-tail, bi-stream and Buneman instabilities. It is noted that these solitary waves can be generated at distant regions far away from the spacecraft locations, because these trapped electrons, or electron holes, are drifting much faster than the local thermal plasmas. Some of the solitary waves are accompanied by perpendicular electric fields indicating that two-or three-dimensional potential structures are passing by the spacecraft. Depending on the local plasma parameters, these multi-dimensional solitary structures couple with perpendicular modes such as electrostatic whistler modes and lower-hybrid modes. In a long time evolution, these perpendicular modes are dissipated via self-organization of small solitary potentials, leading to formation of one-dimensional potential troughs as observed in the deep magnetotail. The above dissipative small-scale processes are reproduced in particle simulations, and they can be used for diagnostics of electron dynamics from spacecraft observation of multi-dimensional solitary waves in various regions of the magnetosphere. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contribution functions for polarized radiative transfer

The concepts of contribution functions (CF) and of mean depths of line formation of unpolarized light as well as of Stokes profiles will be critically discussed. After having outlined the historical development arguments are given in favour of the use of directly observable quantities such as the emergent line intensity or the polarized components seen through polarization optics only. The arguments are provided by a probability interpretation of the CF; the ambiguities of line depression CF as well as some physically strange features in Stokes profiles are avoided if the rules based on this interpretation are observed. Some problems of the interpretation of measurements in chromospheric lines will be discussed as well.     

Manipulator system of the sampling complex of the <Emphasis Type="Italic">Phobos-Grunt</Emphasis> spacecraft

This paper is devoted to the problem of sampling with the use of a manipulator during the mission of the Phobos-Grunt spacecraft. The principle of operation accepted for the chosen engineering solution, as well as the construction of the manipulator scoop, mechanical gears, and the manipulator as a whole, are considered; brief technical specifications are given. The issue of the selection of the soil as an analog of the soil of Phobos to conduct ground-based tests is discussed; the test results and principles of the manipulator operation and control are presented.     

Modern Numerical Schemes for Solving Magnetohydrodynamic Equations

In this paper several modern shock-capturing schemes for solving hydrodynamic and magnetohydrodynamic equations are reviewed. This review covers a wide range of explicit and implicit schemes as well as those in which adaptive mesh refinement methods are adopted. As these numerical schemes are based on Riemann solvers which use Godunov-type techniques, they are well suited for strong shocks and other discontinuities without oscillations in the flow variables. Some other numerical issues as grid generation, divergence cleaning, and an application of MHD schemes to several problems in coronal and interplanetary physics are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.