scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Variability of solar activity and cosmic rays, and their influences on climate change
Miyahara Hiroko 1 , Yokoyama Yusuke 1 , Yamaguchi Yasuhiko 1 , Nakatsuka Takeshi 2 , Horiuchi Kazuho
3 , Fallon Stewart 4 , Matsuzaki Hiroyuki 1
1 2 3 4
The University of Tokyo, Nagoya University, Hirosaki University, The Australian National
University
In this paper, we discuss the long-term variation of solar activity during the last 6000
years, based on the frequency analyses of annually measured carbon-14 content in tree rings.
The long-term variations of solar activity are often reconstructed based on decadal data of
cosmogenit nuclides, however, it is difficult to eliminate the variations caused by the changes
in climate change, anthropogenic effect and the geomagnetic field intensity. So far, multiple
scenarios for the long-term variation of solar activity level have been derived based on
the data sets of cosmogenit nuclides. Our previous studies have shown that the actual length
of solar decadal cycle may be another independent reference for the absolute level of solar
activity. Our records obtained so far indicate that the lengths have varied within 8-15 years
depending on the level of long-term solar activity.
In this paper, we also discuss the variability of the flux of galactic cosmic rays at the earth
related to the variation of solar magnetic activity since the Early Medieval Maximum Period.
We apply the records of multiple cosmogenic nuclides with annual resolution to derive the
information on the variation of incident cosmic rays in the past. The reconstructed variation of
cosmic rays shows that the components of the 11-year and 22-year variations in cosmic rays
vary in time depending on the long-term level of solar magnetic activity. These characteristic
variations of cosmic rays have been also detected in the reconstructed northern hemispheric
temperatures and the humidity change in Japan, and thus it is suggested that cosmic rays are
playing important role in climate change at the hemispheric scale.