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The question is studied whether the one-year solar oscillation found by V. F. Chistyakov for the years 1965–1973 can be traced in the observations of sunspots of 1874–1971 published by Greenwich Observatory. The result is negative. But the study leads to the following two conclusions: (1) The average observable centres of gravity of spot groups are variably displaced towards the central meridian or towards the limb, the time scale of this variability being of the order of 70 years. Thus the angular velocity should be determined from recurrent groups in transit of the central meridian only. (2) The angular velocity will be smaller when determined from older spots.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands. 相似文献
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Andrew Tworkowski Reza Tavakol Axel Brandenburg John M. Brooke David Moss & Ilkka Tuominen 《Monthly notices of the Royal Astronomical Society》1998,296(2):287-295
Axisymmetric mean-field dynamo models in spherical shells are shown to be capable of producing temporally intermittent behaviour. This is of potential importance since (i) it is, as far as we are aware, the first time such behaviour has been produced internally by a mean-field dynamo model in a spherical shell, without requiring any additional assumptions or truncations, and (ii) it may be characteristic of the type of behaviour observed in the long-term record of solar activity, such as Maunder minima. We also show that these types of behaviour persist when the functional form of the alpha quenching is altered and also occur over intervals of the shell thickness and the dynamo number. 相似文献
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Abstract In order to obtain a better insight into the excitation conditions of magnetic fields in flat objects, such as galaxies, we have calculated critical dynamo numbers of different magnetic field modes for spherical dynamos with a flat α-effect distribution. A simple but realistic approximation formula for the rotation curve is employed. In most cases investigated a stationary quadrupole-type solution is preferred. This is a consequence of the flat distribution of the α-effect. Non-axisymmetric fields are in all cases harder to excite than axisymmetric ones. This seems to be the case particularly for flat objects in combination with a realistic rotation curve for galaxies. The question of whether non-axisymmetric (bisymmetric) fields, which are observed in some galaxies, can be explained as dynamos generated by an axisymmetric αω-effect is therefore still open. 相似文献
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Velocities of upper-mantle P waves (Pn) generated by large shallow earthquakes in the Japan area have been studied by the time-term method in three areas of the Japanese islands. Data reported from routinely recording seismic stations, grouped to act as elongated arrays, were used. The velocities observed correspond to the P-wave velocity in the top layer of the mantle. For a region in southwestern Japan not spanned by active volcanoes the value obtained was 8.0 km/s, while for central Japan and on northern Honshu Island the corresponding values were as low as 7.6–7.7 km/s. After allowance for the influence of systematic earthquake mislocation, the probable error of the measurements is estimated not to exceed 0.1 km/s. The differences in P-wave velocity are attributable to the regional variation of subcrustal temperature in Japan reported by Uyeda and Horai, with high temperatures and low velocities in the volcanic zone.The time terms tend to be larger on the Japan Sea side than on the Pacific side of the Japanese islands. We suggest that this is due to an increase in P velocity in the mantle towards the Pacific, perpendicular to our profiles of measurement. 相似文献
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Changes in the duration of the photosynthetically active period strongly influence the changes in the carbon sequestration potential of boreal forests under climatic warming. In this paper, current theories on the effects of environmental variables such as spring air and soil temperature, photoperiod and chilling temperatures on the timing and initiation of photosynthesis in boreal deciduous and coniferous trees are discussed. Different dynamic phenological modeling approaches are reviewed, and model simulations are utilized to demonstrate model predictions under changing climatic conditions. A process-based forest ecosystem model is applied to estimate the relative importance of the duration of the photosynthetically active period on the amount of annual gross primary production and net primary production of boreal coniferous forests. All applied modeling approaches predict an increasing duration of the photosynthetically active period as a result of climatic warming. However, the magnitude of the response to increasing temperature varies between models and therefore affects the predictions of the changes in production. 相似文献
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The N-S drift of sunspot groups has been studied in a different way than previously, using positions of recurrent groups of the years 1874–1976. The existence of the meridional motions, the general shape of the drift curves, and the dissimilarity between these curves around sunspot maxima and minima, are all confirmed. In addition, also for the angular velocity of the Sun the same material gives differences around the times of sunspot maxima and minima. 相似文献
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We have earlier investigated the surface structures of a late‐type, single, giant FK Com for the years 1994–1998 using Doppler imaging. These surface temperature maps revealed long‐lived active regions at high latitudes. Long‐term photometric observations also show that these active regions tend to occur at two permanent active longitudes which are 180 degrees apart from each other, and that the activity switches the longitude with an average period of about 3 years (the “flip‐flop” phenomenon). In this work we present new Doppler maps of FK Com obtained 1998‐2003 and light‐curve maps obtained 2002–2003. These new maps are investigated together with the earlier temperature maps and light‐curve maps, with an aim of further studying the active longitudes, “flip‐flop” phenomenon and surface differential rotation on FK Com. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Raimo Nikkilä Edward Nash Jens Wiebensohn Ilkka Seilonen Kari Koskinen 《International journal of geographical information science》2013,27(6):1210-1226
Rule interchange between information systems is expanding as new interoperable rule formats are emerging from research. However, existing spatial inference systems generally operate on locally stored data with an internal rule format. Consequently, their design offers little support or facilities for rule interchange. This article presents the requirements, components and design for a spatial inference system with rule interchange. Computational efficiency and overall functionality of the design are considered separately, with the latter demonstrated using encoded agricultural legislation and data. A spatial inference system with rule interchange is based on three primary components: rule representation, spatial functionality and data integration. Of these, the interoperable rule representation and data integration distinctly differ from existing spatial inference systems. The presented inference system combines a spatial superset of the W3C Rule Interchange Format (RIF) with full Open Geospatial Consortium simple feature access (OGC SFA) functionality and on-demand data integration utilising Resource Deception Framework (RDF). The design was found to be effective with a computational efficiency depending predominantly on the spatial operations. This design could be further adapted to implement spatial extensions for existing inference systems. Considerable benefits were also discovered when RIF was used as the native language for the inference engine, thereby removing the need for rule transformations and facilitating on-demand data integration with the GML. 相似文献