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We analyze long-term variations of several solar activity indices(AIs) that have been measured over the last 40 years. With this goal, we study the AIs that characterize the fluxes from different areas in the solar atmosphere. Our consideration of mutual correlations between the solar indices is based on the study of relationships between them in the period from 1950 to 1990. This period of time, covering activity cycles 19–22, is characterized by relatively stable relations between the indices. We investigate the normalized variations of these indices in recent time in relation to their values which were calculated by considering radiation from the Sun in the radio range at a wavelength of 10.7 cm(F10.7) in 1950–1990.The analysis of time series, representing variations of the normalized AI(AIFF) in solar cycles 23–24,shows different trends exist for different indices in terms of their long-term behavior. We assume that variations of normalized International Sunspot Number(SSN), F530.3 and Flare Index, which have shown sharp decreases in the last 40 years, are possibly associated with a decrease in the intensity of large-scale magnetic fields in the photosphere(SSN) and in the corona(the coronal index and the Flare Index). 相似文献
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The correlation coefficients of the linear regression of six solar indices versus 10.7 cm radio flux F 10.7 were analysed in solar cycles 21, 22 and 23. We also analysed the interconnection between these indices and F 10.7 with help of approximation by polynomials of second order. The indices we have studied in this paper are: the relative sunspot numbers – SSN, 530.3 nm coronal line flux – F 530, the total solar irradiance – TSI, Mg II 280 nm core-to-wing ratio UV-index, the Flare Index – FI and the counts of flares. In most cases the regressions of these solar indices vs. F 10.7 are close to the linear regression except the moments of time near the minimums and maximums of the 11-year activity. For the linear regressions, we found that correlation coefficients K corr(t) for the solar indices vs. F 10.7 and SSN dropped to their minimum values twice during each 11-year cycle. 相似文献
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Geomagnetism and Aeronomy - Fluxes in flares are studied in soft X-ray (SXR) and extreme ultraviolet (EUV) bands based on data from GOES, the Solar Dynamics Observatory (SDO), and the Thermosphere,... 相似文献
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Geomagnetism and Aeronomy - Various aspects of the of geoefficiency of solar-activity phenomena, such as flares and coronal mass ejections (CMEs), are considered. The number of geoefficient events... 相似文献
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Geomagnetism and Aeronomy - Studies in the extreme ultraviolet (EUV) and X-ray ranges of the solar spectrum are important due to the active role of radiation of these ranges in the formation of the... 相似文献
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The structure and composition of the stellar population in the low-surface-brightness galaxy NGC 5585 is studied using UBV RI CCD photometry. The observations were obtained on the 1.5-m telescope of the Maidanak Observatory of the Astronomical Institute
of the Academy of Sciences of Uzbekistan under conditions with seeing 1.2″–1.8″. A two-dimensional decomposition of the galaxy
emission into bulge and disk components is carried out. Both components have low surface brightnessess. The Sersic parameter
for the bulge is n = 1.2–1.6. The effective radius of the bulge in R and I is equal to the scale length for the brightness decrease in the disk, and comprises 30″–40″ (0.8–1.1 kpc). The spiral arms
seem to form a bar, but the centers of the bar and ring do not coincide with the center of NGC 5585. A powerful star-forming
region is observed 3.2″ (100 pc) from the galactic center, whose radiation swamps the nucleus in the U and B filters. Based on the positions of the various components of the galaxy in two-color diagrams, it is concluded that NGC 5585
has a complex star-forming history that may be different at different distances from the center. 相似文献
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Geomagnetism and Aeronomy - The large (X-ray class > M1) and very large (X-ray class > X1) flares (according to the observations of GOES-15 and Preliminary data from Current Catalog... 相似文献
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V. V. Bruevich A. S. Gusev O. V. Ezhkova F. Kh. Sakhibov M. A. Smirnov 《Astronomy Reports》2007,51(3):222-233
We present the results of U BV RI CCD photometry of giant HII regions in the spiral galaxy NGC 628, acquired with the 1.5 m telescope of the Mt. Maidanak Observatory (Uzbekistan) with an angular resolution better than 1″. We estimate the ages and interstellar extinctions of these regions and identify the acting star-formation mode by comparing the observed color indices with a detailed grid of evolutionary models covering the entire range of parameters of the initial mass function and of ages of the young star-formation complexes, and taking into account two star-formation modes. We find a radial gradient of the interstellar extinction in NGC 628, which is consistent with the radial abundance gradient found earlier by other authors from independent spectrophotometry. Our age estimates agree with abundance estimates from independent observations. 相似文献