HR: 0800h
AN: GP41A-05    [Abstracts]
TI: Long-Term Variations in the Correlations Between Solar Activity, Geomagnetic Activity and Climate - a Link to the Solar Dynamo
AU: * Georgieva, K
EM: kgeorg@bas.bg
AF: Solar-Terrestrial Influences Laboratory, Bl.3 Acad. G.Bonchev str., Sofia, 1113, Bulgaria
AB: Until a few decades ago, the long-term increase in global temperature could be explained to a great extend by the long-term increase in solar activity as measured by the sunspot number, but recently the sunspot number remains nearly constant while global temperature continues increasing. The long-term behavior of the correlation between sunspot number and geomagnetic activity expressed by aa index is very similar. In the 11-year solar cycle, the correlation between aa and sunspot number has been decreasing in the last century, while the lag between their maxima has been increasing. aa can be divided into two components: one due to the solar toroidal field (whose expressions are sunspots and coronal mass ejections, the main source of geomagnetic activity in sunspot maximum), and another due to the solar poloidal field (related to solar coronal holes from which fast solar wind originates, the driver of recurrent geomagnetic activity on the declining and minimum phase of the sunspot cycle). The cyclic transformation of the poloidal field into toroidal field and of this toroidal field into a new poloidal field with the opposite polarity - the solar dynamo, is the basis of solar activity. Here we show that the solar meridional circulation which is a key element in the flux transport dynamo mechanism, has long-term variations determining the long-term variations in solar and geomagnetic activity, and of the correlation between them in the 11-year solar cycle. We study the long-term variations in the poloidal and toroidal components of aa index and demonstrate that the long-term variations in global terrestrial temperature are highly correlated to the long-term variations in the poloidal component of aa, and that using the sunspot number as a measure of solar activity underestimates the role of the Sun in global change.
DE: 1555 Time variations: diurnal to decadal
DE: 1560 Time variations: secular and longer
DE: 1630 Impacts of global change (1225)
DE: 1650 Solar variability (7537)
DE: 2162 Solar cycle variations (7536)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly