Electrical conductivity of rocks in the heating and cooling cycle

Summary The values of the electrical conductivity, recorded during the heating and cooling cycle, of eclogites and basalts are compared. The observed difference in the values is explained by reversible and irreversible changes which take place in the samples.     

On the problem of generalizing Gerstner's trochoidal waves in a three-dimensional case

Summary It is shown that functions, which determine the position of a particle and which represent the solution of Euler's equations of motion in Lagrange's form, can be determined quite accurately from the differential equations established in the paper.     

Apparent radiocarbon ages of recent marine shells from Norway,Spitsbergen, and Arctic Canada

The mean apparent radiocarbon ages of marine shells, colleted alive before the initiation of atomic bomb testing, and also before the main input of dead carbon derived from fossil fuels, are found to be 440 yr for the coast of Norway, 510 yr for Spitsbergen, and 750 yr for Ellesmere Island, Arctic Canada. The relationship between these apparent ages and the oceanic circulation pattern, is discussed. Also possible variations of the apparent ages back in time are discussed.     

Improvement of the geoid in local areas by satellite-to-satellite tracking

Summary The concept of satellite-to-satellite tracking measuring the relative velocity of two orbiting satellites spaced some hundreds kilometers on a close orbit, provides now possibilities for the investigation of the Earth’s gravity field. In the paper only medium and short wave length effects affecting the measured relative velocity have been considered. Collocation is used in such an analysis of local geoid improvement, because this method allows to combine heterogeneous data in a consistent way. Covariance functions relevant for the particular case of a circular equatorial orbit are given. Two kinds of observation equations have been formulated. The choice of observation equation with regard to satellites configuration is discussed. It is found that it is sufficient to have a limited number of satellite-to-satellite observations in a 7^o×7^o area around the estimation point with distances between profiles of about 1^o.5 and between the two satellites forming the pair of 200+350 km; the altitude of satellite-to-satellite observations should be as low as possible. The accuracy of the geoid determination strongly depends on the degree and order of the reference field used. An accuracy of about ±1 m can be achieved with an assumed reference field of (40,40). The influence of measuring errors is discussed and it is shown that only satellite-to-satellite observations with accuracy better then 0.1 mm/sec will give an improvement of the geoid. Finally, some results on the combination of low-low satellite-to-satellite tracking and terrestrial gravity data are given. The proposed method seems to be especially interesting for unsurveyed areas. Furthermore, it has the practical advantage that only a local coverage data is needed.     

Meteorological microseisms and stratospheric warmings

Summary The meteorological microseisms recorded at Prague are found to be essentially independent of the occurrence of the major midwinter stratospheric warmings. This finding contributes to studying the downward propagation mechanism of some extraterrestrial influences.     

Sudden ionospheric disturbances and flare activity in the course of the solar cycle no 20

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The response of the total electron content to the interplanetary magnetic sector boundary crossing

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Relation between the monthly sums of sunshine and global radiation

Summary The statistical treatment of the dependence of monthly sums of global radiation on the monthly sums of sunshine at the stations of Hradec Králové, Bratislava — Koliba and Hurbanovo is presented. The parameters of linear and quadratic regression are derived for the said stations and for the individual months of the year. Drawing on the statistical analysis of the initial data sets, the accuracy and reliability of the mentioned regression relations are critically evaluated.