A Century of Polar Faculae Variations
نویسنده
چکیده
The numbers of faculae at the poles of the Sun have been estimated from white-light images obtained at the Mount Wilson Observatory during 1985–2006 and combined with prior estimates extending back to 1906 when the observations began. The combined data show an 11-yr cyclic variation with faculae maxima occurring during sunspot minima in each of the past 10 sunspot cycles. Also, these numbers of polar faculae are well correlated with the line-of-sight component of the polar magnetic field measured at the Wilcox Solar Observatory since 1976. The numbers of polar faculae show a secular decrease since 1986, suggesting that the polar fields are now weaker than they have been during any cycle in the past century. Subject headings: Sun: corona — Sun: coronal mass ejections (CMEs) — Sun: magnetic fields
منابع مشابه
Zonal Velocity Bands and the Solar Activity Cycle
We compare the zonal flow pattern in subsurface layers of the Sun with the distribution of surface magnetic features like sunspots and polar faculae. We demonstrate that in the activity belt, the butterfly pattern of sunspots coincides with the fast stream of zonal flows, although part of the sunspot distribution does spill over to the slow stream. At high latitudes, the polar faculae and zonal...
متن کاملA model of solar total and spectral irradiance variations
We model solar spectral irradiance variations under the assumption that they are produced by sunspots and faculae alone. The model is based on three components, i.e. quiet Sun, assumed to be temporally invariant, sunspots and faculae whose temporal variations are mimicked using time series of sunspot areas and Mg II core-to-wing ratios. The detailed flux spectrum for each component is employed....
متن کاملDimming of the 17th
Reconstructions of total solar irradiance (TSI) rely mainly on linear relations between TSI variation and indices of facular area. When these are extrapolated to the prolonged 15th–17th century Spörer and Maunder solar activity minima, the estimated solar dimming is insufficient to explain the mid-millennial climate cooling of the Little Ice Age. We draw attention here to evidence that the rela...
متن کاملPhotospheric Faculae and the Solar Oblateness: a Reply to "faculae and the Solar Oblateness" by R. H. Dicke
Dicke has recently contested our statement in an earlier paper that faculae could account for a large part, if not all, of the solar oblateness signal measured by Dicke and Goldenberg in 1966. Using the facular oblateness signal published in our earlier paper and some hitherto unpublished data from his 1966 observations, he concludes that faculae account for only a small part (11 percent) of th...
متن کاملLong-term behavior of emission from solar faculae: steps towards a robust index
Facular emission is one of the major contributors to long-term solar irradiance variations. Reconstructions of past facular variations, however, are strongly hampered by the lack of reliable proxies, particularly on time-scales longer than a solar cycle. We consider the five potential facular proxies with records covering more than 40 years. By suitably weighting and combining them we create a ...
متن کامل