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Reconstruction of the solar activity to 11,000 years BP and possible long-term periodicities
Střeštík, Jaroslav
Observations of solar activity (Wolf sunspot numbers) last only about 250 years, moreover, from sporadic observations the solar activity can be estimated approximately to the year 1500. In addition to the well-known eleven-year period some long-term periods seem to take place. This means that the values at the maxima of 11-yr solar cycles in certain periods are higher than those in other ones. Based on the analysis of dust fallout containing radioactive elements, conserved in glaciers, some authors reconstructed the solar activity first one millennium back, and later more millennia back. The longest series begins 9000 years B. C. and these data are published. Strangely, most authors of these the reconstructions do not look for possible periodicities, or only marginally. Here the possible periodicities obtained from a series of 11,000 years long have been presented. The results suggest a superlong periodicity with the length about 6500 years, on the other hand, they do not confirm variations with the length between 100 and 200 years, which are not persistent.
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Variations with periods near 1.3 year in solar and geomagnetic activity
Střeštík, Jaroslav
The period about 1.3 years, found some time ago in solar wind velocity and in some biological data, is in geomagnetic aktivity prezent only in a short interval after 1990 a in leader extent around 1942. Other periods in the vicinity appear only sporadically and are much weaker. A connection with the solar cycle (even – odd) was not found. In solar acitvity these periods do not appear at all.
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Middle-term changes in the lengths of solar cycles
Střeštík, Jaroslav
In the published data of anuual sunspot numbers since 1500 and less reliable guesses of positions of minima and maxima of solar cycles since 200 B.C. middle-term changes in the cycle lenghts have been investigated. Data published by different authors differ considerably, the more the further to the past they go.
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