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At the solar surface the magnetic field is bundled into discrete elements of concentrated flux, often referred to as magnetic
flux tubes, which cover only a small fraction of the solar surface. Flux tubes span a whole spectrum of sizes, ranging from
sunspots to features well below the best currently obtainable spatial resolution.
Whereas sunspots have been well studied, our knowledge of the true brightness of small-scale magnetic features is hampered
by the insufficient spatial resolution of the observations. A better understanding of the thermal and magnetic properties
of these small-scale features, however, is crucial for an understanding of (climate-relevant) long-term solar irradiance variations. 相似文献
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Most of the present models and reconstructions of solar irradiance use the concept of Photometric Sunspot Index (PSI) to account for the influence of sunspots on solar brightness. Since PSI is based on measured sunspot areas a firm database of such areas is essential. We show, however, that a significant disagreement exists between the data provided by the Royal Greenwich Observatory (from 1874 to 1976) and newer measurements provided by the observatories of Rome, Yunnan, Catania, and the US Air Force. The overlap of the time intervals over which sunspot areas were measured at Greenwich and Rome allows us to quantify the difference between the Greenwich and other data sets. We find that the various data sets differ, at least in a statistical sense, mainly by a correction factor of between 1.15 and 1.25.The revised time series of sunspot areas correlates well with the Zürich sunspot relative numbers over the last 120 years, with the relationship between sunspot areas and sunspot numbers changing only slightly from one cycle to the next. In particular, no indication exists for any extraordinary magnetic behavior of the Sun during the last 2 decades, as might falsely be concluded if the various sunspot area data sets are uncritically combined. There are, however, some indications that cycles 15 and 16 deviate from the rest. We expect that our results should have a significant influence on the reconstruction of the historical solar irradiance. 相似文献
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S. K. Solanki M. Fligge P. Pulkkinen P. Hoyng 《Journal of Astrophysics and Astronomy》2000,21(3-4):163-165
The records of sunspot number, sunspot areas and sunspot locations gathered over the centuries by various observatories are
reanalysed with the aim of finding as yet undiscovered connections between the different parameters of the sunspot cycle and
the butterfly diagram. Preliminary results of such interrelationships are presented. 相似文献
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