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Influence of solar activity variations on the interplanetary space

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Introduction 0 20 40 60 80 100 120 140 160 180 200 1700 1750 1800 1850 1900 1950 2000 year S u n s p o t N u m b e r R Maunder Minimum Dalton Minimum Modern Minimum Figure 1.3. The Sunspot number R series. Here are marked the prolonged solar minima. The most important proxies of the past solar activity are the radionuclides produced by nuclear interactions of CR in the Earth’s atmosphere, in meteorites and in planetary surfaces. In fact the production rate of these cosmogenic radioisotopes depends on the CR flux and energy spectrum of these, in turn, vary in the inner heliosphere dominantly by solar modulation. Therefore, the study of cosmogenic isotopes in terrestrial archives and in meteorites, which fell in different times, gives information on the solar activity in the past. The most useful cosmogenic isotopes in terrestrial archives (independently dated) are 14 C in tree rings and 10 Be in ice cores and sediments. The concentration of the cosmogenic isotopes in these archives is also affected by terrestrial influences such as climatic and geomagnetic field variations (Stuiver and Braziunas, 1993; Lal, 1996). On the contrary, the cosmogenic isotopes in meteorites are produced by CR in the interplanetary space; therefore the production rate of these isotopes does not depend on terrestrial effects. The century scale modulation has been shown in the cosmogenic 44 Ti (T 1/2 = 59.2 yr) activity measured in meteorites which fell in the last two centuries (Bonino et al., 1995; 1999) and in the time series of 14 C in tree rings (e.g. Damon and Sonett, 1991). On this scale during 7

Anteprima della Tesi di Daniele Cane

Anteprima della tesi: Influence of solar activity variations on the interplanetary space, Pagina 5

Tesi di Dottorato

Dipartimento: DIPARTIMENTO DI FISICA GENERALE

Autore: Daniele Cane Contatta »

Composta da 137 pagine.

 

Questa tesi ha raggiunto 346 click dal 20/03/2004.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.