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11.
Geomagnetism and Aeronomy - Solar-climatic correlations were examined over the timescales, corresponding to solar cycles of Schwabe, Hale and Gleissberg, during the last 3–4 centuries using... 相似文献
12.
Two sets of nitrate (NO3
–) concentration data in Central Greenland ice, obtained through the GISP2 collaboration and by the University of Kansas, were analyzed statistically. The two records correlate well over time scales from a few years up to a century. They both contain quasi five-year, decadal and century-type time variations. A quasi five-year periodicity resulting from increases in the mean nitrate concentration before and after maximum sunspot number was confirmed. A tendency of solar proton events to occur more frequently during the rise/decline phases of the solar cycle may cause a quasi five-year variation. Century-type (60–110 yr) variability in nitrate outstrips the corresponding Gleissberg cycle in sunspots by 12–17 years and changes synchronously (correlates with zero phase shift) with the smoothed length of the solar Schwabe cycle. A significant correlation between century-type periodicities for nitrates in Greenland ice and northern Fennoscandian temperatures was established. The results show that despite a strong dependence on local meteorology, nitrate concentration in ice contains valuable information about global geophysical phenomena in the past. 相似文献
13.
Relations between basic indices of the Sun and the cosmogenic isotope 14C and 10Be records were derived using the Artificial Neural Network (ANN) technique. A reconstruction of the sunspot indices and changes
in Total Solar Irradiance (TSI) was carried out. Long-term changes in TSI appear in the amplitude modulation of its 11-year
cyclic variation as well as in its lower envelope describing variability of the background irradiance of the Sun. According
to the reconstruction the irradiance has increased about 2.5 W m−2 since 1441. 相似文献
14.
O.M. Raspopov V.A. Dergachev M.G. Ogurtsov T. Kolström H. Jungner P.B. Dmitriev 《Journal of Atmospheric and Solar》2011,73(2-3):388-399
Unique palaeoclimatic data with annual time resolution as tree ring widths and annual varve deposits are analyzed in order to reveal periodicities in climatic processes at tens to hundreds of million years ago. The climatic periodicities thus found are compared with the solar and climatic periodicities observed at present. 相似文献
15.
In Ostrobothnia, western Finland, buried fossil soils have been recognised in a number of places in the sandy sediments that occur between glaciofluvial deposits and overlying till. Samples from the soil horizons as well as below and above them were taken for optically stimulated luminescence (OSL) dating. The same sites were also sampled for thermoluminescence (TL) dating. Altogether five TL dates and seventeen OSL dates were obtained. The OSL dates can be grouped into two age classes, (i) 120-163 ka and (ii) 76-106 ka, whereas all TL dates are of the order 135-155 ka. A comparison between the results obtained from the two dating methods shows that OSL dates are generally younger than the TL dates for the same sample. The discrepancy may arise partly from problems of setting a correct residual level in TL dating. If this is the case then the TL dates may indicate an upper limit for the true age. The results support the geological interpretation that the fossil soils were formed during the last interglacial, that the soil-forming processes possibly also continued during the first Early Weichselian stadial and interstadial (Brørup sensu lato), and that in general the till-covered glaciofluvial sequences, interpreted as eskers in Ostrobothnia, were deposited during the Saalian or Early Weichselian deglaciation. 相似文献
16.
S. S. Vasiliev V. A. Dergachev O. M. Raspopov H. Jungner 《Geomagnetism and Aeronomy》2012,52(1):121-128
A spectral analysis of data on the flux of cosmogenic 10Be in ice core samples from the Central Greenland (project GRIP) over the last 10 thousand years have been carried out. It
has been shown that the 10Be flux varies cyclically; the most significant cycle is of about 2300 years. Variations in the position of the virtual geomagnetic
pole over 8000 years have been analyzed. Significant components, pointing to the cyclic variation in the position of the geomagnetic
pole with a period of about 2300 years, have been revealed in a periodogram of the virtual geomagnetic pole longitude. In
addition to the nearly 2300-year-long cycle, some lines are observable in the 10Be flux periodogram, which can be considered as a manifestation of the 1000-year-long cycle of the 10Be deposition rate on the ice surface. The relationship between the cyclicity of the geomagnetic pole position and the 10Be flux is discussed. 相似文献
17.
The possible mechanism by which cosmic rays affect the formation of neutral water droplets and ice crystals in the Earth’s
atmosphere has been considered. This mechanism is based on changes in atmospheric transparency and vertical temperature distribution.
It has been indicated that a change in the optical thickness for visible and IR radiation by several percents, which can take
place when cosmic-ray particles penetrate into the atmosphere, results in a change in the temperature vertical distribution,
affecting the growth of water droplets, concentration of active condensation nuclei, and the formation of ice particles. This
mechanism makes it possible to explain the correlation between the intensity of galactic cosmic rays at low altitudes and
the absence of this correlation at middle altitudes. 相似文献
18.
Long-term changes of the GCR intensity in the heliosphere were analysed making use of records of cosmogenic isotopes abundances (10Be and 14C) in natural archives and neutron monitor data. These data contain information about short-term, 11-year, 22-year, centennial and two-centennial cycles of solar activity. A mechanism to explain the long-term modulation of GCR due to changes in the curvature of the interplanetary magnetic field, resulting from changes in solar activity, is suggested. 相似文献
19.
Using proxy series that includes ancient observations of sunspots and auroras, concentrations of cosmogenic isotopes 14C and 10Be, we reconstruct sunspot activity level since 850 AD to the present. As a main reference index of solar activity we use
the Wolf sunspot numbers, which, as we demonstrate, reflect true levels of the activity in the 18th and 19th centuries better
than the Group sunspot numbers. We construct a set of linear and nonlinear inductive models, which are in a good agreement
with each other and reproduce the known global solar activity extrema. According to our results, amplitudes of the global
maxima are in intermediate positions in respect to estimations of other authors. It follows from our reconstructions that
the global maximum of the 20th century is not much higher, if at all, than others. 相似文献
20.
Different records of solar activity (Wolf and group sunspot number, data on cosmogenic isotopes, historic data) were analyzed by means of modern statistical methods, including one especially developed for this purpose. It was confirmed that two long-term variations in solar activity – the cycles of Gleissberg and Suess – can be distinguished at least during the last millennium. The results also show that the century-type cycle of Gleissberg has a wide frequency band with a double structure consisting of 50–80 years and 90–140 year periodicities. The structure of the Suess cycle is less complex showing a variation with a period of 170–260 years. Strong variability in Gleissberg and Suess frequency bands was found in northern hemisphere temperature multiproxy that confirms the existence of a long-term relationship between solar activity and terrestial climate. 相似文献