Long-Term Variation of the Solar Activity and its Possible Connection with the Earth's Climate Condition and Cosmic Ray Modulation

The sun is quite variable in time. When the solar activity is numerated by counting sunspots in number, there exists a so-called eleven year periodicity on the relative sunspot numbers, although this periodicity varies from about 7 to 13 years. The total relative sunspot numbers for respective solar cycles have been increasing almost monotonically for more than 100 years since 1882. This long-term variation as seen on these numbers may have been causally associated with the decrease of the rotation speed at the equator of the sun which has been endured throughout those years since 1882. This long-term increase of the solar activity necessarily introduces its associated increase of the intensity of magnetic field originated from the sun in the inner heliosphere. The intensification of this field seems to strongly influence the behavior of galactic cosmic rays deep in the inner heliosphere and thus indirectly influences the sun - climate condition since the terrestrial climate may be highly dependent in the long-term decrease of the cosmic ray influx into the earth's atmosphere.