明代日食的地方记录

明代中期兴起的地方志和私人著作,记载了许多天象事件,日食记录是其中重要内容.地方性日食记录的精华集中在对日全食现象的生动描述,地方志记录的最大价值是一次日全食的多个见全食点.明代中国东部地区发生了15次中心日食.明后期的10次中,8次都有大量的地方性记录.讨论了明代地方性日食记录的各种特点,并重点展示了这8次日全食在全国各地的观测地点分布以及对日全食景象的生动描述.     

Intricacies of the fine structure of the eclipse corona

The inner white-light corona (up to 2 solar radii) can only be observed during total solar eclipses. New mathematical methods of the corona image processing and digital photo cameras or CCD cameras allow us to detect very faint structures (of a few arcseconds) in this part of the corona, even from images taken with relatively small telescopes (1–2 meters in the focal length). In the present paper we will discuss such structures as observed during the last few solar eclipses, mainly those of 2001 and 2006. Obtained results show that the white-light corona is highly structured not only in the sense of a variety of different types of its classical “objects”, e.g., polar plumes, helmet streamers, threadlike streamers, etc, but also within these objects themselves. Voids, loops, radial and non-radial threads, and other yet-undefined dark structures (“empty space”?) are well visible especially inside helmet streamers. This strongly indicates that the classical picture of the corona characterized by a hydrostatic distribution of density and temperature is no longer a sufficient assumption. It is magnetic forces that play a dominant role in shaping and structuring this part the corona. Given a remarkable similarity between the EUV corona as observed by SOHO and the white-light corona observed by us during the above-mentioned eclipses up to two solar radii. We suggest that the “missing” observations of the white-light corona should be replaced by those of the EUV one. Moreover, the last eclipse’s observations also indicate that the knots of some prominences extend well into the white-light corona. So, the next total eclipses of the Sun, of 1 August 2008 and 22 July 2009, offer an excellent opportunity for preparing joint observations for space-borne and ground-based eclipse teams.     

Statistical analysis of geomagnetic field variations during the partial solar eclipse on 2011 January 4 in Turkey

Some geophysical parameters, such as those related to gravitation and the geomagnetic field, could change during solar eclipses. In order to observe geomagnetic fluctuations, geomagnetic measurements were carried out in a limited time frame during the partial solar eclipse that occurred on 2011 January 4 and was observed in Canakkale and Ankara, Turkey. Additionally, records of the geomagnetic field spanning 24 hours, obtained from another observatory(in Iznik, Turkey), were also analyzed to check for any peculiar variations. In the data processing stage, a polynomial fit, following the application of a running average routine, was applied to the geomagnetic field data sets. Geomagnetic field data sets indicated there was a characteristic decrease at the beginning of the solar eclipse and this decrease can be well-correlated with previous geomagnetic field measurements that were taken during the total solar eclipse that was observed in Turkey on 2006 March 29. The behavior of the geomagnetic field is also consistent with previous observations in the literature. As a result of these analyses, it can be suggested that eclipses can cause a shielding effect on the geomagnetic field of the Earth.     

八世纪前中国纪时日食观测和地球转速变化

本文对中国正史记载的八世纪前的３４次纪时日食观测作了分析，指出其中两次日食记载有重复，另一次纪日不确。对３２次日食观测记录的１４个食分和４５个见食时刻作了考查，其中除一次食甚时刻误差较大（约１＾ｈ）外，余皆准确可靠。本文据此对地球自转速率的长期变化趋势作了探讨。     

Scientific observations at total solar eclipses

The occasion of the longest totality of an eclipse in the 18 yr 111/3 d saros cycle leads to taking stock of the scientific value of ground-based eclipse observations in this space age. Though a number of space satellites from the U.S., Europe, Japan, and Russia study the Sun, scientists at eclipses can observe the solar chromosphere and corona at higher spatial resolution, at higher temporal resolution, and at higher spectral resolution than are possible aloft. Furthermore, eclipse expeditions can transport a wide variety of state-of-the-art equipment to the path of totality. Thus, for at least some years to come, solar eclipse observations will remain both scientifically valuable and cost-effective ways to study the outer solar atmosphere.     

日食的射电观测(英)

日食为射电天文提供了一维高空间分辨率太阳射电观测机会．日食射电观测在太阳射电物理的发展上起过重要的作用．文中对日食射电观测的若干重要因素作了介绍和分析．日食射电观测在我国太阳射电天文发展上也起了重要作用．文中简要介绍了在我国组织观测的1958年、1968年、1980年及1987年的太阳射电日食观测及其主要结果．     

带食而出的天光变化

作为“夏商周断代工程．天再旦”研究的一部分,讨论带食而出的天光变化．用照相机测光的方法测定正常日出前后的天光变化规律,建立带食而出的天光视亮度变化计算方法,并给出计算“天再旦”现象的范围和强度的方法．为此于1997年3月9日在新疆组织了群众性的日食观测．实测证实带食而出的确可以引起“天再旦”现象,同时与理论计算有很好的符合.     

夏商周断代工程及其天文学问题

《夏商周断代工程》由文献,考古,古文字,碳14测年和天文学待方面的专家联合攻关,致车于推进我国早期年代学研究的发展,天文学在五星聚合,三代大火,国外天象,仲康日食,夏小正,禹伐三苗,甲骨文天象,武王伐纣,天再旦,金文历谱,周代历法,计算中心等专题中起了主要或重要作用,天文方法确定的宾组月食,武王伐纣和天再旦年代被作为断代工程结论而采用,成为夏商周年的重要支撑点,铜器铭文中的朋相记录也是西周列王年代的重要依据。     

《授时历》预报2012年日食

元代郭守敬等1280年编制的《授时历》是中国本土科学家研制的最后一部历法,具有极高的精度。采用其仍可预报2012年5月21日发生的日食,其预报北京地区的见食情况时食甚时刻误差4 min,食分误差为0.04。给出了《授时历》推步的1990～2050年北京的见食情况及精度,其中食甚时刻的标准偏差为103.04 min,食分的标准偏差则不低于0.33。通过考察1280～2050年间186个日食计算结果,可得出《授时历》自行用以来推步日食的误差,考虑到存在错报(不可见)和漏报因素的影响,其食甚时刻和食分的标准偏差分别不低于50.65 min和0.19;同时指出,随着行用时间的延长其推时误差也逐步放大。     

The Measurement of Solar Diameter and Limb Darkening Function with the Eclipse Observations

The total solar irradiance varies over a solar cycle of 11 years and maybe over cycles of longer periods. Is the solar diameter variable over time too? A discussion of the solar diameter and its variations must be linked to the limb darkening function (LDF). We introduce a new method to perform high-resolution astrometry of the solar diameter from the ground, through the observations of eclipses, using the luminosity evolution of Baily’s bead and the profile of the lunar edge available from satellite data. This approach unifies the definition of the solar limb with the inflection point of LDF for eclipses and drift-scan or heliometric methods. The method proposed is applied for the videos of the eclipse on 15 January 2010 recorded in Uganda and in India. The result suggests reconsidering the evaluations of the historical eclipses observed with the naked eye.     

Analysis of geomagnetic effect of previous 5 solar eclipses occurring in China during past 50 years

In this paper results and analysis of geomagnetic observations during previous 5 solar eclipses occurred in China are summarized. They are solar eclipses: No. 1, on 19 June 1936 in Heilongjiang of NE China; No. 2, on 21 September 1941 in Fujian; No. 3, on 19 April 1958 in Hainandao; No. 4, on 22 September 1968 in Xinjiang; and No. 5, on 16 February 1980 in Yunnan of SW China. The authors took part in the last 2 expeditions and joint programmes in the track of totality.The methods of evaluation for eclipse effects on the geomagnetic field are briefly described both for the quiet and disturbed days. The discussion of these data is made with reference to Chapman's theoretical consideration on optical eclipse effect, together with the quiet-day overhead current systems in the upper atmosphere. We conclude that optical eclipse effects are easily observable under favourable conditions, and further observations are essential to establish the yet unknown effects due to corpuscular eclipses.     

Ancient Chinese observations of physical phenomena attending solar eclipses

The realization that solar activity probably undergoes changes in qualitative character on time scales greater than the 11 or 22 year cycle but short compared to the duration of recorded history gives renewed importance to historical documents describing the state of solar activity. Modern eclipse observation reveal the presence of solar activity through the appearance of coronal structures and prominences. It has been widely remarked that eclipse records prior to the 18th century are uniformly silent on these conspicuous solar eclipse features, raising the possibility, however unlikely, that a change in solar activity has occurred which rendered them only recently noticeable. We present here material from ancient Chinese sources, primarily astrological, that describe phenomena attending solar eclipses that are almost certainly coronal structures and prominences. Thus, these aspects of the present character of solar activity have apparently occurred at other times in history, if not continuously.     

中国早期日食记录研究进展

中国古代系统的日食记录始自春秋。自汉以至清代,整齐而完备。此前的夏、商、西周三代,日食记录零散而模糊。历来研究者众而难得定论。近年来由于天文计算方法和历史年代学的进展,早期日食记录的研究也获得新的成就。     

Variation of the solar diameter from solar eclipse observations, 1715–1991

The diameter of the Sun may be measured at the time of a solar eclipse. We have performed an exhaustive search of the astronomical literature to find all existing observations of solar eclipses suitable for this purpose. We have also taken new observations by new techniques. We have undertaken a project to reduce them systematically, and in an automated, self-consistent way. This will produce determinations of the solar radius at the times of solar eclipses from 1715 to the present. Re-reduction, using newer ephemerides, of observations made in 1984 shows that the component of the residuals caused by the ephemeris is substantially reduced. This paper summarizes the research plan, outlines the detailed astronomical features included in the calculations, and presents the results available.     

The first experience of solar eclipse observations with a miniature torsion balance

We observed the behavior of the pointer of an asymmetric torsion balance (TB) at solar eclipse dates and on other off-eclipse days. A peculiar reaction of the miniature TB different from its reaction at off-eclipse time was recorded for some solar eclipses. The relative positions of the Earth, Moon, and Sun are among the possible factors affecting the position of the TB pointer. A time shift between the maximum phase of a solar eclipse and the maximum TB reaction was detected. We conclude that base observations of such phenomena from different points of the terrestrial globe are necessary.     

On the nature of the unique eclipsing system H 187 (HMW 15)

We present our photometric observations of the T Tauri star H 187. They confirm our conclusion that a new extended eclipse has begun in this young object. By the end of 2005, H 187 reached its minimum light following which its brightness began to slowly increase. Comparison with the previous ～3.5-yr-long eclipse observed by Cohen et al. shows that the new eclipse follows the previous eclipse fairly closely and, hence, it was caused by a second passage of the same extended dust or gas-dust cloud around the object. We have estimated the period between these events to be 4.7 yr. The object reddened during the eclipse, suggesting that the extinction was produced by small grains ～0.1μm in size. Possible mechanisms of such unusual eclipses are discussed. We draw an analogy between these eclipses and the cycles of photometric activity observed in UX Ori stars. Light curves similar to those observed for H 187 are shown to be obtained in the model of a young binary system with a low-mass companion accreting matter from the remnants of a protostellar cloud at a rate of ～10^?9 M _⊙ yr^?1.     

Mutual eclipses of J2 Europa by J1 Io observed at Yunnan Observatory in 2009

Mutual events between natural satellites include mutual occultation and mutual eclipse. Mutual eclipse is another kind of mutual occultation as viewed from the center of the Sun instead of the Earth. Two mutual eclipses of J2 Europa by J1 Io (2009 Aug. 28 and Sept. 12) were observed at Yunnan Observatory during the PHEMU09 international campaign. We will calculate the astrometric data of these Galilean satellites by analyzing and fitting the light curves we obtained. The limb-darkening was considered during...     

WHITE-LIGHT POLARIZATION AND LARGE-SCALE CORONAL STRUCTURES

The results of the white-light polarization measurements performed during three solar eclipses (1973, 1980, 1991) are presented. The eclipse images were processed and analysed by the same technique and method and, consequently, the distributions of the polarization and coronal intensity around the Sun were obtained in unified form for all three solar eclipses. The mutual comparisons of our results, and their comparison with the distributions found by other authors, allowed the real accuracy of the current measurements of the white-light corona polarization, which is not worse than ±5%, to be estimated. We have investigated the behaviour of the polarization in dependence on heliocentric distance in helmet streamers and coronal holes. Simultaneous interpretation of the data on polarization and intensity in white-light helmet streamers is only possible if a considerable concentration of coronal matter (plasma) towards the plane of the sky is assumed. The values obtained for the coronal hole regions can be understood within the framework of a spherically symmetrical model of the low density solar atmosphere. A tendency towards increasing polarization in coronal holes, connected with the decrease of the hole's size and with the transition from the minimum to the maximum of the solar cycle, was noticed. The problem of how the peculiarities of the large-scale coronal structures are related to the orientation of the global (dipole) solar magnetic field and to the degree of the goffer character of the coronal and interplanetary current sheet is discussed briefly.     

Probing the Fundamental Physics of the Solar Corona with Lunar Solar Occultation Observations

Imaging and spectroscopy of the solar corona, coupled with polarimetry, are the only tools available at present to capture signatures of physical processes responsible for coronal heating and solar wind acceleration within the first few solar radii above the solar limb. With the recent advent of improved detector technology and image processing techniques, broad-band white light and narrow-band multi-wavelength observations of coronal forbidden lines, made during total solar eclipses, have started to yield new views about the thermodynamic and magnetic properties of coronal structures. This paper outlines these unique capabilities, which until present, have been feasible primarily with observations during natural total solar eclipses. This work also draws attention to the exciting possibility of greatly increasing the frequency and duration of solar eclipse observations with Moon orbiting observatories utilizing lunar limb occultation of the solar disk for coronal measurements.