The Sun-Earth connection in time scales from years to decades and centuries

The Sun-Earth connection is studied using long-term measurements from the S un and from the Earth. The auroral activity is shown to correlate to high a ccuracy with the smoothed sunspot numbers. Similarly, both geomagnetic acti vity and global surface temperature anomaly can be linked to cyclic changes in the solar activity. The interlinked variations in the solar magnetic ac tivity and in the solar irradiance cause effects that can be observed both in the Earth's biosphere and in the electromagnetic environment. The long-t erm data sets suggest that the increase in geomagnetic activity and surface temperatures are related (at least partially) to longer-term solar variati ons, which probably include an increasing trend superposed with a cyclic be havior with a period of about 90 years.