A study of Sq variation at Addis Ababa

We analyse the Sq variation at Addis Ababa, Ethiopia for 1958 through 1973. The increase in importance of the semidiurnal H field relative to the diurnal H field during low sunspot years reflects an enhanced counter-electrojet effect at such times. The range of H exhibits a direct sunspot influence for all seasons, and the e-season range dominates over that of the d and j seasons. The Z and D field components are little influenced by sunspot occurrence and in both cases the range of the j season dominates over that of the e and d seasons. The daytime relation between H and Z variations is needle-shaped, indicating that changes in Z are proportional to changes in H; the night-time relation is quite complex.     

Geomagnetic field variation and the equivalent current system generated by an ionospheric dynamo at the solstice

The geomagnetic field variation and equivalent current system produced by an asymmetrical ionospheric dynamo action under a solstitial condition are simulated and compared with the observational results. Results of our simulation reproduce well most of the observational features of the solstitial Sq system. For example, the latitude of the current vortex center is higher in summer than in winter and the local time of the center in the summer hemisphere is located earlier than that in the winter hemisphere. In the morning and afternoon sector the current vortex in the summer hemisphere invades the winter hemisphere. The first feature is attributed to the ionospheric currents, but the second and third features are due to the field-aligned currents generated by the asymmetry of the ionospheric dynamo.     

The equatorial electrojet and the day-to-day variability of Sq

The day-to-day variability of Sq(H) at equatorial stations has been studied, using the correlation between daily ranges for the IQSY at a large number of pairs of stations. It is found that the daily ranges at stations under the equatorial electrojet are significantly less well correlated with those at other equatorial stations than is the case for pairs of equatorial stations not involving an electrojet station, for comparable distances of separation of the pairs of stations.     

The day-to-day variability of Sq in geomagnetically conjugate areas

The correlation of daily ranges of Sq(H) has been found to be slightly but significantly greater for pairs of stations which are approximately at magnetically conjugate locations than for other, non-conjugate pairs of similar distance of separation. It is suggested that the effect is due to field-aligned currents.     

Simulation of ionospheric currents and geomagnetic field variations of Sq for different solar activity

Variations of ionospheric Sq electric currents and fields caused by changes in electric conductivity due to changes in solar activity are studied using the International Reference Ionosphere (IRI) model. Calculations are made for R (sunspot number) = 35 and 200 on the assumption of constant (1, −2)mode tidal winds. It is shown that electric fields grow when solar activity is high, because the ratio of the conductivity in the F-region to that in the E-region increases. Currents in the F-region become stronger than those in the E-region, and nocturnal currents are not negligible when solar activity becomes high. F-region currents also play an important role in the westward currents on the high latitude side of the current vortex. The calculated geomagneticH component at the equator has a depression around 1600 LT for R = 35, while it decreases smoothly from 1100 LT to 1900 LT for R = 200. This difference is consistent with the observed geomagnetic field variation. The ratio of total Sq currents obtained by our simulation is about 3.5, which is a little larger than is found in the observed results.     

Determination of the latitude of Sq focus and its relation to the electrojet variations

The latitude of the Sq focus is determined analytically using the method of natural orthogonal components. Geomagnetic data along the 75°E meridian have been used. The day-to-day variations of the latitude of the Sq focus thus determined are very highly correlated with the electrojet enhancements. The strength of the normal Sq field and the electrojet field are not correlated. It appears that as the Sq focus moves towards the equator the entire current pattern bodily moves equatorwards with an increased current concentration in the electrojet region.     

An empirical study on the modification of China's current urban social security system

This study challenges the conventional correlation between economic performance and the level of the development of social security systems. By focusing on China's urban areas, we provide an overview of the components and benefits, from a comparative perspective, of China's current social security system. We also create a comprehensive and generally applicable method using factors such as economics and population, among others, as standards to evaluate the efficacy of China's system. In order to demonstrate our primary hypothesis – that the Chinese Communist Party government has to modify its social security system to adapt to or bring about changes in the basis of its legitimacy – we analyse Chinese social security records and other related data after 1949 by statistical methods. The formula we provide in this study can be used to forecast China's expenditure on its urban social security system, and other scholars can apply our methods to countries in which conditions are broadly similar.     

岁时——传统中国人的时间体验

如风岁月,如梦年华,是人们对时间流逝的体验与感叹,这是用心去度量时间。时间本身并无质感,时间是一个不能用感官感受却又能体验到的实在,我似对时间的把握,只有通过特殊的标识才能实现,正如英国人类学家利奇所说：“其实我们是通过创造社会生活的间隔来创造时间的。在这样做之前是没有时间可以测量的。”岁时就是中国人创造的时间分隔的独特方式,岁时观念体现了传统中国人对时间的特殊体验。     

史前时期的梳子

根据考古发现,早在距今6千多年以前的史前时代,我们的祖先就开始使用梳子了。在源远流长的历史长河中,梳子与当时的社会生活息息相通,揭示了它们在数千年发展过程中的演进轨迹,可以帮助我们从一个侧面认识人类物质文化发展的历程。因此,本文主要依据考古发掘的资料,试对史前时期梳子的形制、结构以及功能等相关问题进行探讨。     

赋予时间意义——以历史意识为概念基础的普遍分类学

以下观点①来自对历史编纂学的比较研究。有一种原则把过去理解为历史。在这种原则或至少类似原则基础的化背景中,比较研究很容易就可以做到。以比较的方法对西方历史思维进行的基本研究和解释已经开展,但是从一种跨化的比较角度看待过去的方法(这种方法导致了历史思想的产生)进行比较就有更大的难度。     

The current state of American archaeology

Meltzer, David J., Don D. Fowler, and Jeremy A. Sabloff. American Archaeology Past and Future: A Celebration of the Society of American Archaeology 1935–1985. Washington, D.C.: Smithsonian Institution Press, 1986. 479 pp. including illustrations and chapter references. $35.00 cloth, $19.95 paper.

Schiffer, Michael B. Advances in Archaeological Method and Theory. Volume 9. Orlando, Florida: Academic Press, 1986. v + 468 pp. including illustrations, tables, chapter references, and index. $75.00.