Computation of the atmosphere-less light intensity curve during a total solar eclipse by using Lunar Reconnaissance Orbiter topography data and the DE430 astronomical ephemeris

Observations of the sky irradiation intensity in the visible wavelengths during a solar eclipse permit to model the Sun diameter,a key number to constrain the internal structure of our star.In this paper,we present an algorithm that takes advantage of the precise Moon topography from Lunar Reconnaissance Orbiter to compute,with a high resolution in time,the geometrical part(i.e.top-of-atmosphere,and for a given wavelength)of the sky irradiation at any given location on the Earth during these events.The algorithm is also able to model the Baily’s beads.We give as an application the theoretical computation of the light curve corresponding to the solar eclipse observed at Lakeland(Queensland,North Australia)on 2012 November 13.The application to real data,with the introduction of atmospheric and instrumental passbands,will be considered in a forthcoming paper.     

A long time span relativistic precession model of the Earth

A numerical solution to the Earth’s precession in a relativistic framework for a long time span is presented here.We obtain the motion of the solar system in the Barycentric Celestial Reference System by numerical integration with a symplectic integrator.Special Newtonian corrections accounting for tidal dissipation are included in the force model.The part representing Earth’s rotation is calculated in the Geocentric Celestial Reference System by integrating the post-Newtonian equations of motion published by Klioner et al.All the main relativistic effects are included following Klioner et al.In particular,we consider several relativistic reference systems with corresponding time scales,scaled constants and parameters.Approximate expressions for Earth’s precession in the interval±1 Myr around J2000.0 are provided.In the interval±2000 years around J2000.0,the difference compared to the P03 precession theory is only several arcseconds and the results are consistent with other long-term precession theories.     

LO And: an A-subtype contact binary with a very cool third component

Despite the intensive investigations since the discovery of LO And approximately 60 yr ago, its evolutionary status and subtype are still a matter of controversy. By simultaneously modeling the radialvelocity curves and new light curves with the Wilson-Devinney code, we present new geometric,photometric and absolute parameters for this system. The simultaneous solution suggests that LO And is an A-subtype contact binary with a contact degree of 32.4%. The absolute parameters are modified to become M_1= 1.409 M⊙, M_2= 0.449 M⊙, R_1= 1.36 R⊙and R_2= 0.83 R⊙. From our observations and data from surveys, we determined 334 eclipse timings. The O-C diagram, constructed from the new eclipse timings and those reported in the literature, reveals a secular increase and a cyclic variation in its orbital period. The former is caused by conservative mass transfer from the secondary component with less mass to the primary one with more mass. The latter may be explained by either the cyclic magnetic activity on the two components or the light-time effect due to a third body. With the absolute physical parameters,we investigated its evolutionary status, and find that LO And is an unevolved contact binary undergoing thermal relaxation oscillation, which will eventually coalesce into a single star with rapid rotation.     

An Ancient Solar Eclipse Record “Tian-da-yi“ in the 10th Century BC

The ancient record“Tian-da-yi“(the sky darkened greatly )is identified with the solar eclipse on May 31,976BC.This identification is demonstrated in this paper through a palaeographic ,astronomical and chronological analysis,It is probably the earliest solar eclipse in Chinese histroy that can be so identified.     

Elliptical distortion of the Milky Way's rotation traced by high-mass star-forming regions

The gravitational potential of the Milky Way is non-axisymmetric, caused by a bar or triaxial halo, which dominates elliptical rotation of the Milky Way. Employing a likelihood analysis, we exploit the astrometric data of masers thoroughly and constrain the elliptical rotation of the Galaxy. Masers in high-mass star-forming regions, observed by VLBA, are more distant tracers than stars observed in the optical bandpass,and thus are more appropriate for studying the global feature of the Milky Way's rotation. A clear elliptical potential of the Milky Way is detected, with an ellipticity of €_0~0.09 at the Sun, and the ellipticity increases towards the outer disk. The minor axis of the elliptical potential(the major axis of the rotation orbit) is found to be near the Sun with a displacement of ~32°. Based on the rotation model assumed for an elliptical potential, we also make a kinematical calibration of the Galactocentric distance of the Sun, which gives R_0= 7.63 ± 0.34 kpc.     

Properties of filaments in solar cycle 20-23 from McIntosh Archive

A filament is a cool, dense structure suspended in the solar corona. The eruption of a filament is often associated with a coronal mass ejection(CME), which has an adverse effect on space weather. Hence,research on filaments has attracted much attention in the recent past. The tilt angle of active region(AR)magnetic bipoles is a crucial parameter in the context of the solar dynamo, which governs the conversion efficiency of the toroidal magnetic field to poloidal magnetic field. Filaments always form over polarity inversion lines(PILs), so the study of tilt angles for these filaments can provide valuable information about generation of a magnetic field in the Sun. We investigate the tilt angles of filaments and other properties using McIntosh Archive data. We fit a straight line to each filament to estimate its tilt angle. We examine the variation of mean tilt angle with time. The latitude distribution of positive tilt angle filaments and negative tilt angle filaments reveals that there is a dominance of positive tilt angle filaments in the southern hemisphere and negative tilt angle filaments dominate in the northern hemisphere. We study the variation of the mean tilt angle for low and high latitudes separately. Investigations of temporal variation with filament number indicate that total filament number and low latitude filament number vary cyclically, in phase with the solar cycle. There are fewer filaments at high latitudes and they also show a cyclic pattern in temporal variation. We also study the north-south asymmetry of filaments with different latitude criteria.     

A New Analysis in the Field of the Open Cluster Collinder 223

The present study of the open cluster Collinder 223 (Cr 223) depended greatly on the photoelectric data of Claria and Lapasset. We use the data in conjunction with the AAO/DSS^1 image of the cluster in a re-investigation to improve the main parameters of Cr 223, including the stellar density, the position of the cluster‘s center, the cluster‘s diameter. Its luminosity function, mass function, and total mass are also estimated.     

Electromagnetic effects on the orbital motion of a charged spacecraft

This paper deals with the effects of electromagnetic forces on the orbital motion of a spacecraft.The electrostatic charge which a spacecraft generates on its surface in the Earth’s magnetic field will be subject to a perturbative Lorentz force.A model incorporating all Lorentz forces as a function of orbital elements has been developed on the basis of magnetic and electric fields.This Lorentz force can be used to modify or perturb the spacecraft’s orbits.Lagrange’s planetary equations in the Gauss variational form are derived using the Lorentz force as a perturbation to a Keplerian orbit.Our approach incorporates orbital inclination and the true anomaly.The numerical results of Lagrange’s planetary equations for some operational satellites show that the perturbation in the orbital elements of the spacecraft is a second order perturbation for a certain value of charge.The effect of the Lorentz force due to its magnetic component is three times that of the Lorentz force due to its electric component.In addition,the numerical results confirm that the strong effects are due to the Lorentz force in a polar orbit,which is consistent with realistic physical phenomena that occur in polar orbits.The results confirm that the magnitude of the Lorentz force depends on the amount of charge.This means that we can use artificial charging to create a force to control the attitude and orbital motion of a spacecraft.     

Data preprocessing and preliminary results of the Moon-based Ultraviolet Telescope on the CE-3 lander

The Moon-based Ultraviolet Telescope(MUVT) is one of the payloads on the Chang'e-3(CE-3) lunar lander. Because of the advantages of having no atmospheric disturbances and the slow rotation of the Moon, we can make long-term continuous observations of a series of important celestial objects in the near ultraviolet band(245～340 nm), and perform a sky survey of selected areas, which cannot be completed on Earth. We can find characteristic changes in celestial brightness with time by analyzing image data from the MUVT, and deduce the radiation mechanism and physical properties of these celestial objects after comparing with a physical model. In order to explain the scientific purposes of MUVT, this article analyzes the preprocessing of MUVT image data and makes a preliminary evaluation of data quality. The results demonstrate that the methods used for data collection and preprocessing are effective, and the Level 2A and 2B image data satisfy the requirements of follow-up scientific researches.     

The Kinematic Theory of Solar Dynamo

Generation of the Sun‘s magnetic fields by self-inductive processes in the solar electrically conducting interior, the solar dynamo theory, is a fundamentally important subject in astrophysics. The kinematic dynamo theory concerns how the magnetic fields are produced by kinematically possible flows without being constrained by the dynamic equation. We review a number of basic aspects of the kinematic dynamo theory, including the magnetohydrodynamic approximation for the dynamo equation, the impossibility of dynamo action with the solar differential rotation, the Cowling‘s anti-dynamo theorem in the solar context, the turbulent alpha effect and recently constructed three-dimensional interface dynamos controlled by the solar tachocline at the base of the convection zone.     

Solar flare high-energy electron spectra

The Moon's umbral shadow, tangentially penetrating the Earth's atmosphere, appreciably reduces the brightness of the twilight sky at points located under the shadow axis. This should yield favourable conditions for observation of the zodiacal light for small altitudes of the Sun below the horizon. The location of the projection of the Moon's shadow axis at the Earth's surface under the above conditions is calculated for the case of the total solar eclipse of 30 June, 1992.     

中国古历经朔数据的恢复及应用

中国元代的《授时历议》保存了44部古历的推朔参数及比验资料．借助古代朔望计算方法：1）恢复了诸历行用初年的天正经朔数值；2）修正了史载的错误数据．3）根据Meeus方法计算出经朔的理论值，并由此确定古历经朔的推步精度；4）尝试应用这些数据考察地球自转长期变化，得出日长变化为1．8ms／cy．     

天再旦日食的根据与计算——对Keenan质疑的注释

作者由“天再旦”日食说证实西周懿王元年为公元前 899年。夏商周断代工程以此为支点之一 ,得到西周年代表。针对读者的质疑 ,在历史文献的可靠性、天光视亮度的表达和计算方法、地球自转长期参数等方面做了进一步的阐述。     

Differential Rotation Driven by Precession

The tidal force in the Earth–Moon system exerted on the Earth's equatorial bulge results in the Earth's precession. It was proposed a long time ago that the strong shear flow driven by the precession of the Earth may power the Earth's dynamo in its liquid core. We present a nonlinear analytical study investigating how the Poincaré force in a rotating, precessing spherical system drives a large-amplitude differential rotation which plays a major role in the modern theory of the geodynamo. The analysis is based on a perturbation approach in terms of the small Poincaré force parameter. It is found that the amplitude of the precession-driven differential rotation is consistent with that estimated from the geomagnetic secular variation.     

Simultaneous spectroscopic and photometric observations of binary asteroids

Abstract— We present results of visible wavelengths spectroscopic measurements (0.45 to 0.72 microns) of two binary asteroids, obtained with the 1‐m telescope at the Wise Observatory on January 2008. The asteroids 90 Antiope and 1509 Esclangona were observed to search for spectroscopic variations correlated with their rotation while presenting different regions of their surface to the viewer. Simultaneous photometric observations were performed with the Wise Observatory's 0.46 m telescope, to investigate the rotational phase behavior and possible eclipse events. 90 Antiope displayed an eclipse event during our observations. We could not measure any slope change of the spectroscopic albedo within the error range of 3%, except for a steady decrease in the total light flux while the eclipse took place. We conclude that the surface compositions of the two components do not differ dramatically, implying a common origin and history. 1509 Esclangona did not show an eclipse, but rather a unique lightcurve with three peaks and a wide and flat minimum, repeating with a period of 3.2524 hours. Careful measurements of the spectral albedo slopes reveal a color variation of 7 to 10 percent on the surface of 1509 Esclangona, which correlates with a specific region in the photometric lightcurve. This result suggests that the different features on the lightcurve are at least partially produced by color variations and could perhaps be explained by the existence of an exposed fresh surface on 1509 Esclangona.     

A study of the γ-ray flux during the total solar eclipse of 1 August 2008 at Novosibirsk,Russia

In the past, there have been reports of the observation of decrease in the flux of secondary cosmic γ-rays during a total solar eclipse. We have measured the flux of secondary cosmic γ-rays during the total solar eclipse that occurred at Novosibirsk in Russia, on 1 August 2008. Highly sensitive measurements were carried out by using a detector system with built-in redundancy. The system consisted of two independent, large volume NaI(Tl) scintillator detectors for sensitive and reliable measurements. The data display significant variability in the flux of secondary γ-rays in the energy range 50–4600 keV. Just prior to the total solar eclipse a change ∼9% in the flux was observed, followed by a small but steady decrease ∼4% during the eclipse. The temporal variation in the observed flux of γ-rays were found to be nearly identical for the two detectors. The energy dependence of the variation was further studied by binning the yield in three energy ranges, namely, 100–200, 200–400 and 400–4600 keV. The nearly identical time variation observed in the two independent measurements provides confidence that the measured variation is real and not an artifact of the instrumentation. Systematic observations during the future eclipses are required to study this fascinating phenomenon which is not yet understood.     

On using the beaming effect to measure spin-orbit alignment in stellar binaries with Sun-like components

The beaming effect (aka Doppler boosting) induces a variation in the observed flux of a luminous object, following its observed radial velocity variation. We describe a photometric signal induced by the beaming effect during eclipse of binary systems, where the stellar components are late type Sun-like stars. The shape of this signal is sensitive to the angle between the eclipsed star’s spin axis and the orbital angular momentum axis, thereby allowing its measurement. We show that during eclipse there are in fact two effects, superimposed on the known eclipse light curve. One effect is produced by the rotation of the eclipsed star, and is the photometric analog of the spectroscopic Rossiter-McLaughlin effect, thereby it contains information about the sky-projected spin-orbit angle. The other effect is produced by the varying weighted difference, during eclipse, between the beaming signals of the two stars. We give approximated analytic expressions for the amplitudes of the two effects, and present a numerical simulation where we show the light curves for the two effects for various orbital orientations, for a low mass ratio stellar eclipsing binary system. We show that although the overall signal is small, it can be detected in the primary eclipse when using Kepler Long Cadence data of bright systems accumulated over the mission lifetime.     

大气对地球自转变化的影响-方法和数据的深入分析

大气相对固体地球的运动产生大气相对角动量，它的变化可以激发地球自转多时间尺度的变化．计算大气相对角动量现在采用两种不同的垂直积分高度，一种为从地形表面积分到顶层大气，称之为SP方法；另一种为从1000hPa积分到顶层大气，称之为BP方法，对采用这两种方法所得到的大气相对角动量进行了详细的比较．应用欧洲中距气象预报中心（ECMWF）和美国国家环境预报中心（NCEP）大气再分析数据，重新研究了大气相对角动量变化的时空特征．通过对大气相对角动量季节平均，季节振幅和时空特征的分析，得出ECMWF和NCEP的大气相对角动量变化对地球自转周年极移的影响，在亚洲季风区域和南极洲区域差别最为明显．     

Observational Study about the Influence of the Solar Wind on the Earth's Rotation

The data on the variation of the Earth's rotation from IERS and the parameters of the solar wind measured by IPM 8 from July 1992 to September 1995 were used for a regression analysis. The results show that there seems to be a weak linear correlation between the velocity of the solar wind near the Earth, V, and the variation of the length of the day, lod₁ calculated from UT1 and averaged over five days. The correlation coefficient is R=0.186. The preliminary conclusion is that the Earth's rotation could be influenced by the variation of the velocity of the solar wind with a short time scale of several days.     

明代大食分日食记录考证

自明代开始,地方志中出现大量的日食记录,其中全食、近全食记录对于现代天文学研究具有特殊意义．明代此类记录共有270条,由于流传中的混淆,其中大半错误．现以（中国古代天象记录总表｝为基础,根据现代天文学计算结果和原文的文字特征,对每一条记录进行考证和说明,试图恢复记录原貌,以便使其中宝贵的信息得以应用。