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.     

8.6毫米波段太阳射电亮度温度分布

本文根据１９８０年２月１６日的８．６毫米波长射电日食观测资料，计算了太阳射电辐射的亮度温度的径向分布，由日食过程的第一，第二和第三接触的计算结果表明，在日面光学边缘内侧的二角分范围内，均存在明显的单峰状增亮结构。三个接触的平均增亮峰值约为１８％，增亮区的射电辐射占日面总辐射的４％。日食当天在８．６毫米波段上测得的日面平均亮度温度为９７２７Ｋ。     

上海天文台佘山工作站夜天亮度的变化

使用1994—2007年在1．56m反射望远镜CCD照相机拍摄的资料，测定了上海天文台余山工作站夜天亮度的变化。由于上海城市的发展，佘山工作站的夜天亮度在V波段从每平方角秒约19mag变到15．8mag，也就是说，夜天亮度自1994年以来变亮了约20倍。国际上优良台站的夜天亮度在V波段等于或暗于21．5mag。上述夜天亮度是优良台站的200多倍。现在在佘山工作站使用1．56m反射望远镜对暗于V=14mag的星做精确测光已经很困难了。     

LONG-TERM VARIATIONS OF THE TORSIONAL OSCILLATIONS OF THE SUN

We investigated long-term variations of the differential rotation of the solar large-scale magnetic field on 1024 H charts in the latitude zones from +45° to -45° in the period 1915–1990. We used the expansion in terms of Walsh functions. It turns out that the rotation of the Sun becomes more rigid than average during the cycle maximum and the rotation is more differential during minimum. From 1915 to 1990, 7 bands of faster- and 7 bands of slower-than-average rotation are revealed showing an 11-year period. These bands drift towards the equator: 45° in 2.5 to 8 years. The time span of the bands varies from 4 to 6.8 years and is in anti-phase with long-term solar activity. The latitude span of the bands of torsional oscillations varies from 0.5 R to 1.3 R and shows a long-term variation of about 55 years. The poloidal component of velocity, V varies from 2 ms ^-1 to 6 ms ^-1. The maximum rate of the equatorial drift occurs in the period between 1935 and 1955 and it develops prior to the highest maximum activity. At the modern epoch from 1965 to 1985, V does not exceed 3 ms ^-1, but now it has a tendency to increase. The bands of slower-than-average rotation correspond to the evolution of the magnetic activity towards the equator in the butterfly diagram.     

EMCep的快周期光变

１９９０年和１９９２年本文作者用北京天文台兴隆站６０厘米反光望远镜对Ｂｅ星ＥＭＣｅｐ作了ＵＢＶ光电测光，取得数据２７７组。结合历年来文献给出的光变极小时刻数据作了Ｏ－Ｃ分析，得到了改进的周期为０．８０６１８４天或单波周期为０．４０３０９２天。分析还表明可能存在周期变快的趋势，且周期变率ｄＰ／ｄｔ＝－８．８５１４×１０－１０；光变曲线的形状呈现出极小阶段尖锐而极大阶段较宽。此外Ｕ－Ｂ色指数随光变周期位相有可察觉的变化。     

自由地核章动的时变特性

对VLBI观测确定的IAU1980章动模型的天极偏移序列进行分析,结果显示自由地核章动在1990年以前的幅值比其后为强,其时变强度比周年受迫章动的为大．另外,小波变换的时频谱分析结果显示在天极偏移序列中存在一幅值约0．1毫角秒的准两年周期信号．仅从目前的数据分析结果尚不足以确定此信号与顺向自由地核章动之间的关系,进一步的观测检,验和深入的内核动力学研究是非常必要的．     

SS433短周期变化中的拍现象

本文用喷流模型计算SS433短周期变化的周期和振幅值。讨论短周期变化叠加成拍的条件。用此条件判断,很自然地得出:在短周期变化中可能存在拍现象。对于喷流模型,在一个进动周期内其拍频为2。 文中还利用了Margon,B·等人的SS433多普勒频移图作SS433多普勒频移的残差分布图。在分布图中,某些进动周期内显示出分布轮廓有双峰结构,分析产生双峰的原因,正是与章动有关的、短周期变化中的拍现象。因此,在SS433的163天多普勒频移图上,观测点始终存在10％的弥散,乃是163天进动曲线与不能消除的短周期中的拍叠加的结果。 这样,本文从理论和实测分析上都证认了SS433短周期变化中存在拍现象的可能性。     

PREDICTIONS OF THE FEATURES FOR SUNSPOT CYCLE 23

Smoothed monthly mean Ap indices are decomposed into two components (Ap) _c and (Ap) _n. The former is directly correlated with the current sunspot numbers, while the latter is shown to achieve its maximum correlation with the sunspot numbers after some time lag. This latter property is used to develop a method for predicting the sunspot maximum based on the observed value of (Ap) _n maximum which occurs during the preceding cycle. The value of R _M for cycle 23 predicted by this method is 149.3 ± 19.9. A method to estimate the rise time (from solar minimum to maximum) has been developed (based on analyses of Hathaway, Wilson, and Reichmann, 1994) and yields a value of 4.2 years. Using an estimate that the minimum between cycles 22 and 23 occurred in May 1996, it is predicted that the sunspot maximum for cycle 23 will occur in July 2000.     

由PREM模型参数计算地球自转的周期变化

弹性地球在日月引潮力势作用下的形变引起其转动惯量的改变，从而导致地球自转速率的变化．本文利用PREM地球模型所给的物质密度和弹性等参数分布．计算日月引潮力势产生的地球形变附加势，进而计算转动惯量的变化．最后得到一系列包含周期同引潮势带谐项、振幅大于1微秒的自转速率周期变化系数．     

INTER-CYCLE VARIATIONS OF SOLAR IRRADIANCE: SUNSPOT AREAS AS A POINTER

Most of the present models and reconstructions of solar irradiance use the concept of Photometric Sunspot Index (PSI) to account for the influence of sunspots on solar brightness. Since PSI is based on measured sunspot areas a firm database of such areas is essential. We show, however, that a significant disagreement exists between the data provided by the Royal Greenwich Observatory (from 1874 to 1976) and newer measurements provided by the observatories of Rome, Yunnan, Catania, and the US Air Force. The overlap of the time intervals over which sunspot areas were measured at Greenwich and Rome allows us to quantify the difference between the Greenwich and other data sets. We find that the various data sets differ, at least in a statistical sense, mainly by a correction factor of between 1.15 and 1.25.The revised time series of sunspot areas correlates well with the Zürich sunspot relative numbers over the last 120 years, with the relationship between sunspot areas and sunspot numbers changing only slightly from one cycle to the next. In particular, no indication exists for any extraordinary magnetic behavior of the Sun during the last 2 decades, as might falsely be concluded if the various sunspot area data sets are uncritically combined. There are, however, some indications that cycles 15 and 16 deviate from the rest. We expect that our results should have a significant influence on the reconstruction of the historical solar irradiance.     

全球水分布和气压变化对固体地球质心位置的影响

根据IERS决议,国际地球参考系的原点是地球固体部分、海洋和大气的共同质量中心因此,地球上流体部分质量分布变化会改变固体地球质心相对于国际地球参考系原点的位置变化．空间技术如SLR和GPS的观测结果表明,固体地球质心可能有幅度达10毫米的位置变化,所以给出固体地球质心位置变化以及地球物理原因已成为重要问题.本文采用了全球4000多个地面气象台站从1949到1982年的月平均降水、温度和气压值,对水和大气的分布变化引起的固体地球质心位置变化进行了计算,得出水储量分布变化对固体地球质心运动比气压分布变化有更大的贡献,固体地球质心位置变化的最大值可达4毫米．     

PETROLOGICAL FEATURES OF SHOCK METAMORPHISM IN CHONDRITES: ALFIANELLO

The Alfianello meteorite was inspected by optical microscopy, both by transmitted and reflected light, in order to look for evidence of shock metamorphism. The stone is a well-recrystallized olivine-hypersthene chondrite that shows unambiguous features of dynamic deformation. Some examples of planar deformation structures, which are notable in olivine and plagioclase feldspar crystals, are reported. The presence of several shock-transformed components is described in some detail. Alfianello appears to belong to a class of chondrites lightly-to-moderately shocked.     

具有硅酸盐尘埃特征碳星的新的候选者

本文根据红外天文卫星的宽波段测光及低分辨率光谱资料，给出了两颗新的可能具有硅酸尘埃特征的碳星及４颗可能的候选者。     

用Hamilton方法计算滞弹地球自转的潮汐变化

在日月引潮力势作用下地球产生弹性形变．地幔粘滞性子致这个形变对于引潮力滞后,成为引起地球自转长期减慢的原因之一．地幔滞弹性也使有效洛夫数k增加,并使自转变化的周期项位相滞后,即产生反常位相项．本文首先用Hamilton方法计算了地球的形变．然后考虑到地幔的滞弹性,计算了在日月引潮力作用下的地球自转长期减慢和滞弹性对周期（带谐）变化的影响．     

类星体0917＋62快速射电变化和星际折射闪烁

本文分析类星体０９１７＋６２在波长６ｃｍ和１１ｃｍ上快速变化（时标１天）的结构函数．讨论在什么条件下，这种快速变化可用星际折射闪烁来解释．结果表明，折射闪烁解释对星际介质和射电源结构提出了相当明确的限制：散射介质应为连续介质，其有效距离应０．４ｋｐｃ；射电源应包含０．０５—０．１ｍａｓ的致密结构．对快变射电源方向上脉冲星的测量以确定星际介质特性和用ＶＬＢＩ测量快变射电源中的小角径成分，将是检验星际折射闪烁解释的必要途径．     

上海天文台1.56米反光镜ThomsonCCD系统的性能变化

上海天文台１ ．５６ 米反光镜于１９９１ 年引入的Ｔｈｏｍｓｏｎ １０２４ ×１０２４ＣＣＤ 系统,到１９９８ 年３ 月已满７ 年。本文对此ＣＣＤ 系统的某些性能变化做了讨论。     

INTEROBJECT STRUCTURE OF UNGROUPED IRON METEORITES AS REVEALED BY ADVANCED CLUSTERING: METHODS AND CHEMICAL FEATURES

Using the MASLOC clustering strategy, 61 ungrouped iron meteorites are probed for physico-chemical clusters. The existing classification of 13 resolved chemical groups is used as an internal coherence reference. Results include tentative establishment of a new group: ID (7 members), with chemical features similar to those of the non-magnetic groups IAB and IIICD. Six additional pairings, all with magmatic chemical signatures, are also recognized.     

A SEARCH FOR VECTOR MAGNETIC FIELD VARIATIONS ASSOCIATED WITH THE M-CLASS FLARES OF 10 JUNE 1991 IN AR 6659

A careful analysis of a 6-hour time sequence of vector magnetograms of AR 6659, observed on 10 June 1991 with the MSFC vector magnetograph, has revealed only minor changes in the vector magnetic field azimuths in the vicinity of two M-class flares, and the association of these changes with the flares is not unambiguous. In this paper we present our analysis of the data which includes comparison of vector magnetograms prior to and during the flares, calculation of distributions of the r.m.s. variation of the azimuth at each pixel in the field of view of the active region, and examination of the variation with time of the azimuths along the flaring neutral lines and at every pixel covered by the main flare emissions as observed with the H telescope coaligned with the vector magnetograph.     

CHEMICAL VARIATIONS AMONG L-CHONDRITES—IV. ANALYSES,WITH PETROGRAPHIC NOTES,OF 13 L-GROUP AND 3 LL-GROUP CHONDRITES

We review our procedures for selecting, preparing and analyzing meteorite samples, present new analyses of 16 ordinary chondrites, and discuss variations of Fe, S and Si in the L-group. A tendency for Fe/Mg, S/Mg and Si/Mg to be low in L chondrites of fades d to f testifies that post-metamorphic shock melting played a significant role in the chemical diversification of the L-group. However, these ratios also vary widely and sympathetically in melt-free chondrites, indicating that much of the L-group's chemical variation arose prior to thermal metamorphism and is in that sense primary. If all L-chondrites come from one parent body, type-correlated chemical trends suggest: 1) that the body had a traditional “onion skin” structure, with metamorphic intensity increasing with depth; and 2) that it formed from material that became more homogeneous, slightly poorer in iron, and significantly richer in sulfur as accretion proceeded.