大气反常折射对星表和参考系的影响

在过去的时间纬度工作中,对大气反常折射的研究证明,大气反常折射给时问纬度测量带来了严重的影响。而当时大多数星表的编制都是时间纬度测量的副产品,无疑大气反常折射也给这些星表带来严重的误差影响。过去我国的经典天体测量工作以测时、测纬为主,这一问题并没有得到重视。在星表和参考系工作已成为我国基本天休测量工作的一项主要内容的今天,对大气反常折射的测量与研究,尤其对有效的测量应得到足够的重视。作者根据自己的实际测量和研究指出,大气反常折射主要由观测室周围不良小气候的造成,其中以具有周年变化和周日变化的大气反常折射对初始星表系统的影响最为严重。并分别讨论了这种反常折射对子午星表、等高星表和参考系的影响,提出了今后开展这方面工作的建议。     

徐家汇观象台天文测时的季节性变化

中星仪测时的组内符合程度比组外符合程度约高一倍,这已是人所共知的事实.一般认为引起组外符合程度较差的因素是仪器情况的变更和反常折射的存在.本文根据1951—1954年间徐台的天文测时结果求出它的季节性变化,并考虑星表误差、反常折射以及其他气象因素在测时结果所引起的影响.在上述期间,徐台天文测时所用的是一具口径80mm 焦距86cm 的帕兰(Prin)中星仪,附有马达带动人手操纵的接触测微器,仪器的水平轴是用水银盘控制的.主要的观测者为龚惠人(K),沈祖耀(S),罗定江(L)三人.     

全球光学时纬仪器1992—1994年观测初步分析

概述了1992－1994年全球光学时纬仪器获得的测量资料，其中包括每架仪器的观测组数和测时、测纬精度，并且给出了按仪器类型统计的观测组数及测时、测纬精度。     

天文是纬残差波动异常的一种可能的地球物理解释

天文国介一般都从地球大气的局部运动来解释天文时纬残差波动的原因，但长期得不出确定的结论。本文从残差波动异常同台站周围强震活动的关系出发，论述了地下物质运动与构造活动也是产生天文时纬波动异常的可能原因，其中的关键是地方铅垂线的变化。作者认为，天文时纬仪器的特长是能检测铅垂线的连续变化，若经改进，它即能铅垂线的变化，又能对地震预测提供有益的信息。     

天文折射的光谱型效应

天文折射中包含有显著的光谱型效应。本文从有效波长的角度,讨论了光谱型效应的复杂性,不同的仪器采用不同的接受器、以及在不同的天顶距观测,都有不同的光谱型差。提出在低纬子午环上,对不同光谱型的天体测定出天文折射,以提高星位测定的精度。     

研究大气反常折射的迫切性

就地球大气对天体测量观测的影响作了分类，介绍了对各类影响的传统处理方法，也介绍了低纬子午环的分别对待方法，特别强调了短周期的和不规则的反常折射影响对提高观测精度的限制，并提出了测定这些影响的可能途径。     

测定天文大气折射和建立电磁波折射延迟实测模型(Ⅵ)-瞬时大气折射值和折射率差的取得

根据测定天文大气折射的原理,叙述了利用相应的观测值获得瞬时大气折射测定值和建立大气折射实测模型的途径,并从各种测定值与最后结果之间的关系,指出了这里对数据处理的要求;文章介绍了对测定值进行波长改正和建立折射延迟实测模型的处理方法,分析了改正模型对天文大气折射测定值的分布要求,给出了观测数据随天顶距的增大而加密的分布模型。     

天文实测蒙气差的研究

建立在子午—卯酉交替观测原理基础上的低纬子午环（ＬｏｗＬａｔｉ－ｔｕｄｅＭｅｒｉｄｉａｎＣｉｒｃｌｅ）即将出厂投入调试及试运行阶段，进一步研究天文蒙气差修正将是低纬子午环进行高精度观测的重要保证之一。作为对天文蒙气差修正的初步研究，本文首先分析了影响天文蒙气差的主要气象因素，对蒙气差随各种条件的变化情况进行了讨论；在此基础上，推算了大气平面平行层模型以及同心球层模型下的蒙气差值，论述了蒙气差表的编制方法，进而对各种蒙气差理论公式计算所得的修正值进行了分析比较；针对理论计算蒙气差值精度的不足，本文着重阐述了利用低纬子午环（ＬＬＭＣ）进行大气蒙气差实测的方法、原理，较为详尽的说明传统的方法不能满足实测大气折射的要求，而低纬子午环由于自身一些新的特点，能够满足Ｔｅｌｅｋｉ所提出的四个要求；在此基础上推导了相应的计算公式并进一步探讨了实测大气等密度倾斜的方法，最后给出了相应的精度估计，就如何建立一个适合于观测点的实用的实测大气模型进行了探讨     

射电天文及卫星测地中大气折射的改正及其精度

本文综述了电离层、对流层中电波折射引起的射电天文观测及卫星测地中的各种误差及各种改正方法和它们的精度。 对流层影响的主要改正方法是实测大气温度、压力等参数,用数学模型计算。电离层影响的改正目前有三种方法:一是实时测量电离层主要参数——电子总含量的变化,然后用数学模型方法改正。二是采用双频同时观测的手段来消除电离层折射的影响。三是采用自校准方法。文中还比较了两种不同的自校准方法——常规自校准方法和多余量自校准方法。     

光学天文时纬残差异常在强震预测中的实践——纪念唐山地震暨光学天文时纬残差异常发现40周年

为了进一步研究光学天文时纬残差异常在地震预测中的作用,介绍了光学天文时纬残差震前异常的发现和在地震预测中的研究实践,以及云南天文台光电等高仪的时纬残差异常变化与其周邻强震的对应关系,最后以讨论的形式给出了这种关联的可能的地球物理机制,目前在地震预测中的局限性和可能的解决途径。重要的是,2010年以来的预测实践进一步表明,利用光学天文时纬残差的同步异常提供地震预测信息,既没有虚报,也没有漏报。这就说明,它是完全可以作为地震预测的一种手段,投入地震预测实践中,值得更多重视和更加深入的研究。     

Excitation of Annual Polar Wobble by Global Oceans

A reasonable and quantitative result on the variation of polar wobble excited by the oceans is not available at present. Numerous researches have shown that atmospheric motion is the greatest excitation source for the seasonal variations in the polar wobble and that oceanic motion is one of the main remaining excitation sources. The excitation of variation in the annual polar wobble caused by oceans from 1992 to 2004 both globally and in latitude dependence, have been studied in depth by means of the new generation of SODA oceanic data assimilation (SODA-1.4.2 and SODA-1.4.3) and the ECCO oceanic data assimilation. The result shows that the variation in the seasonal polar wobble excited by the SODA oceans is very close to that of the residual after the action of the atmosphere and land water is deducted from the geodesic excitation function for a large part of the investigated time interval, and that there is overall agreement between the two as regards the annual amplitude and phase. In addition, in comparison with the result of early SODA-Bata 7, the new generation of SODA oceanic excitation has achieved obvious improvements. The latitude distributions of the excitations of the annual polar wobble by the SODA and ECCO oceans are consistent in the Greenwich direction, while having obvious differences in the direction of 90° E.     

Chandler wobble in variations of the Pulkovo latitude for 170 years

The work studies the Chandler component of polar motion, obtained from variations in the Pulkovo latitude over 170 years (1840–2009). To extend the time series of variations in the Pulkovo latitude back into the past until 1840, we used the first Pulkov observations on the basis of the Reynolds transit instrument in the prime vertical and on the basis of large vertical Ertel circle. We employed different methods of analysis of nonstationary time series, such as wavelet analysis, methods of bandpass filtering, singular spectral analysis, and Fourier and Hilbert transforms. Changes in the Pulkovo latitude from 1904–2006, as inferred from ZTF-135 observations and as calculated from international data, were compared. It was shown that time changes in the amplitude and phase of Chandler polar motion can be studied based on long-term observation time series of latitude at a single observatory, even if these observation records have gaps. We were the first to study the changes in the Chandler wobble for that long time series of variations in the Pulkovo latitude with the help of different methods. The long observation record and the methods of analysis of nonstationary time series had allowed us to identify two similar structures, both well apparent during the periods of 1845–1925 and 1925–2005 in the time variations of phase and amplitude. The presence of this structure indicates that low-frequency regularities may be present in the Chandler polar motion, and one of the manifestations of this may be the well known feature in the region of 1925. The superimposed epoch method was used to estimate the period of variations in the amplitude with a simultaneous change of phase of this oscillation, which was found to be 80 years. In addition, advantages of singular spectral analysis for studying the long-period time series with involved structure are demonstrated.     

Annual and semi-annual zonal wind components and corresponding temperature and density variations, 60–130 km

From rocket and radar-meteor wind observations, annual and semi-annual components of the zonal flow are derived for latitudes N at heights between 60 and 130 km. Height regions of maximum and minimum amplitude are described with reference to changes in phase. The annual components decrease with height throughout the mesosphere and, after a reversal of phase, enhance to 25 m/sec at 100 ± 5 km. The semi-annual components have maximum amplitudes of 25 m/sec over a wide range of latitude in two height regions at 90 and 120 km and in a limited range of latitude (near 50°) at 65 km.

Calculated temperatures and log densities are discussed in terms of amplitude and phase as functions of height and latitude. Below 100 km a comparison is made with temperature amplitudes derived from independent temperature data. Above 100 km the annual temperature variation maximizes at 115 km and is particularly large at high latitudes (exceeding 50°K). On the other hand, the semi-annual component increases rapidly with height between 110 and 120 km at all latitudes maximizing at the 120 km level, where amplitudes exceed 25°K at high and low latitudes and 10°K at mid-latitudes. The annual component of log density, like the temperature variation, is largest at high latitudes up to 125 km. The semi-annual variation has a minimum at 110–115 km, above which amplitudes increase with height, reaching 5–12 per cent at 130 km according to latitude. The phases at and near 130 km for the annual and semi-annual density variations are very close to those found at greater heights from satellite orbits and amplitudes could be readily extrapolated to agree with those in the satellite region.     

Influence of imf sector polarity on annual and diurnal variations of absorption in the auroral zone

The effect of the polarity of the interplanetary magnetic field (IMF) on the absorption in and near the auroral zone has been studied using measurements from a meridional chain of riometers in Finland in the years 1973–1978. The measured absorption values were divided into two groups, corresponding to away and towards polarities of the IMF, and the values of absorption were examined for the two groups separately. The annual means of absorption were found to be independent of sector polarity in the whole latitude range. In the annual and diurnal variations a polarity effect could be found down to L =4.4, in the annual variation some remnants of it down to L = 3.4. In the annual variation, the towards (T) polarity is associated with a strong spring maximum and the away (A) polarity with a fall maximum in absorption. The diurnal variations are most pronounced during T polarity in the spring and during A polarity in the fall, with high daytime maxima in both cases, suggesting that the loss processes of trapped electrons in the day sector might be modulated by IMF polarity. Our analysis reveals the effect of the different components of the IMF; The annual variations show the effect of the vertical component (varying energy transfer from the solar wind into the magnetosphere) and the diurnal variations in the equinoxes the effect of the azimuthal component (shift of the absorption zone along the dawn-dusk meridian).     

Early latitude observations at the Pulkovo observatory

Pulkovo astrometric observations began in the 1840s using the Repsold transit instrument in the prime vertical and Ertel vertical circle. The first observers on these instruments were W.I. Struve, 1840–1856, and Kh.I. Peters, 1842–1849. In the present work, we collected and analyzed different series of latitude variations from observations made by M.O. Nuren, B. Wanach, A.A. Ivanov, I.N. Bonsdorf, and A.Ya. Orlov. In addition, results are given of investigations of a specific behavior of the Chandler polar motion in this interval, obtained by C. Chandler, Ivanov, Kh. Kimura, Orlov, and N. Sekiguchi. The aim of this paper is to search for and analyze the earliest series of Pulkovo latitudes, in order to evaluate the possibility of their use to study the motion of the pole at the maximum available range of observations. Different methods were used to isolate and analyze the sum of Chandler and annual latitude variations. The annex provides a series of Pulkovo latitude variations for 1840–1848, which may be used to extend latitude variation back to 1840.     

Spatial and temporal variations in the solar brightness

We have investigated long-term variations of solar brightness as a function of both time and solar latitude using eight years of ground-based photometric data in conjunction with space-based irradiance data. In particular, we have examined whether the combination of sunspot brightness deficits and facular brightness excesses is sufficient to explain the solar cycle irradiance variations. After correcting for the contribution from sunspots, we find that the irradiance data can be adequately explained by a model in which the remaining brightness variations are due entirely to facular contributions confined to the magnetically active latitudes. Thus we find no support for the hypothesis that there are convectively driven hot bands in the active latitudes, and our data show brightness variations that are well described by a facular contrast function.     

Annual and sub-annual effects of EUV heating—II. Comparison with density variations

By a detailed comparison of annual and sub-annual components of EUV absorption heat input with those of the Jacchia density models, we consider the importance of EUV heating in the annual and sub-annual variations of the upper atmosphere. When all the geometrical effects of EUV heat input have been taken into account, it is found that a remarkable correspondence exists between properties of each harmonic component of EUV heat input and Jacchia model temperature and densities. Equinoctial latitude independence of diurnal averaged annual and sub-annual components of heat input and density is proposed as a test of the significance of the EUV heat input. The Jacchia model is found to satisfy this test rigourously.     

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.     

Reduction of ephemeris error influence in determinations by lunar laser ranging

It has been shown in different previous papers that continuous or quasi continuous ranging at a lunar reflector from a terrestrial observatory will yield the distancew of that observatory to Earth instantaneous axis of rotation, and its longitudeL with respect to Ephemeris meridian. However it has been shown also that these determinations imply a very accurate knowledge of the geocentric range of the same reflector. By developing the difference: true minus computed geocentric ranges as a function of time, we establish relations between the first and second order terms of the above development and the errors entailing the longitude and distance to axis determinations, respectively.On the other hand, the different terms of that same development are related to the first, second, ... variations of true minus computed geocentric ranges of the reflector during lunar passage. Thus, the first two differences are finally related to errors committed onL andw determinations.The above properties have been extended to higher order variations. We show that, as could be expected, those with odd order correlate with longitude errors, and those with even order with distance to axis errors.Inasmuch as the magnitude of successive terms can be expected to decrease as their order increases, it appears thus that the most accurate determinations forL andw should rely on higher order variations, calling for range measurements in large number and evenly distributed during Moon passage.At the same time, comparison betweenw andL values resulting from variations of the same parity but different orders will provide a coherence test for such determinations.Communication presented at the conference on Lunar Dynamics and Observational Coordinate Systems held January 15–17, 1973 at the Lunar Science Institute, Houston, Tex., U.S.A.