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801.
802.
The mean width and distribution of penumbral filaments of a sunspot have been estimated, using white light photographs obtained with a vacuum, Newtonian type, telescope. Three areas corresponding to the penumbra of a sunspot have been analysed. Data were collected during the solar eclipse of June 1973. The photometric profiles of the Moon limb over the photosphere have been analysed to obtain useful information on both, atmospheric and instrumental perturbation on each exposure. The mean value of the width of penumbral filaments is 0.37 arc sec.Now at INTA-Villafranca, S.T.S., P.O. Box 54065, Madrid, Spain. 相似文献
803.
Continuous measurements of the geomagnetic field variations at ground stations are important to investigate several aspects of magnetospheric dynamics related to variations in the solar wind conditions which, ultimately, originate from the Sun. We present a comparative analysis of geomagnetic field measurements at several ground stations with simultaneous magnetospheric and interplanetary observations in order to understand the origin and characteristics of the observed fluctuations. The results suggest that long period geomagnetic field fluctuations can be directly driven by solar wind density fluctuations at the same frequencies via the modulation of the magnetopause current. We also discuss the possible occurrence of additional contributions related with cavity/waveguide resonances of the entire magnetosphere as well as those of resonance processes of the geomagnetic field lines. 相似文献
804.
O. V. Verkhodanov V. V. Sokolov M. L. Khabibullina S. V. Karpov 《Astrophysical Bulletin》2010,65(3):238-249
We analyze the randomness of the sky distribution of cosmic gamma-ray bursts. These events are associated with massive galaxies,
spiral or elliptical, and therefore their positions should trace the large-scale structure, which, in turn, could show up
in the sky distribution of fluctuations of the cosmicmicrowave background (CMB). We test this hypothesis by mosaic correlation
mapping of the distributions of CMB peaks and burst positions, find the distribution of these two signals to be correlated,
and interpret this correlation as a possible systematic effect. 相似文献
805.
806.
Abdel-Fattah Attia 《Experimental Astronomy》2016,42(3):343-359
The paper presents an adaptive particle swarm optimization (APSO) as an alternative method to determine the optimal orbital elements of the star η Bootis of MK type G0 IV. The proposed algorithm transforms the problem of finding periodic orbits into the problem of detecting global minimizers as a function, to get a best fit of Keplerian and Phase curves. The experimental results demonstrate that the proposed approach of APSO generally more accurate than the standard particle swarm optimization (PSO) and other published optimization algorithms, in terms of solution accuracy, convergence speed and algorithm reliability. 相似文献
807.
Detailed photometrical monitoring of the cataclysmic variable SDSS J080434.20+510349.2 began at the Crimean Astrophysical Observatory (Ukraine) and the Apache Point Observatory (United States) before the 2006 outburst, continued during the outburst, as well as the following two years. We established the unique nature of the primary and secondary components of the binary. We performed a comprehensive study of the white dwarf’s pulsations over the course of five months, two years after the 2006 outburst. It is shown that the most stable pulsations are equal to or double a period of 12.6 min. On the basis of all the available observations, more precise values for the orbital and the superhump periods were found to be 0.0590048(3) days and 0.059729(4) days, respectively. Our estimation of the mass of the secondary component lies in the range of solar mass from 0.037 to 0.087. This confirms the previous suggestion that the secondary component is most probably a brown dwarf. 相似文献
808.
We present new in situ measurements of solar wind electron density as a function of heliolatitude. The data were obtained on Ulysses during its fast transit from south solar pole to north solar pole, at heliocentric distance about 1.5 AU, near the 1996 solar activity minimum. The density is measured accurately using the method of quasi-thermal noise spectroscopy with the Ulysses radio experiment, at a higher time resolution than the particle analysers on board. At low heliolatitudes (22° S to 21° N) the histogram of our data shows three main classes of flows with densities centered at 3.5, 7, and 12 cm-3, close to the values previously found by near-ecliptic space probes, in the region where fast coronal hole wind alternates with slower streamer belt wind. Poleward of 22° latitude where Ulysses encountered fast wind coming from coronal holes, the histogram of our data shows a single class of flow centered at 2.9 cm-3 with a roughly normal distribution. We find a density nearly independent of latitude, with the mean density from the south coronal hole 10% larger than that from the north, which may stem from a genuine north/south asymmetry and/or from the small decrease in solar activity during the time of the observations. We finally compare the data with some analytical models. 相似文献
809.
810.
Leroy, Bommier, and Sahal-Bréchot (1984) determined the vector magnetic field in a large sample of quiescent prominences. The direction of the axial component is in general subject to a 180 deg uncertainty. We have selected those prominences in the sample whose field direction is unambiguous. For 95 such prominences, only 3 do not obey the hemispheric preferences of sinistral or dextral filaments, discovered by Martin, Tracadas, and Billamoria (1994). No explanation for the exceptional cases was found.A search of the Ottawa River Solar Observatory archives was made to check on the structural signatures of sinistral and dextral filaments. Of 32 filaments in common with the Leroy data set, 12 were classifiable as sinistral or dextral from their H fine structure and of these, 3 were exceptions to the hemispheric rule.Thus only a small percentage of quiescent filaments disobeys the hemispheric rule. 相似文献