... Future seminars . ... Long -term evolution of 27 days signal in solar activity and terrestrial magnetic indices - common features and differences ". ... The 27-day signal created by the solar rotation is reflected by the 27-day geomagnetic signal. We study the long-term evolution of the 27 days signal and compare its properties for solar and geomagnetic activity. ... We obtain that 'short' and 'long' period in the 27-days range are differently reflected in the solar and geomagnetic activity. ...