Long-term variations of polar magnetic flux of the Sun and terrestrial climateLong-term variations of polar magnetic flux of the Sun and terrestrial climate
Faculty of Sciences. Physics
Department of Physics
SOLSPA 2001: proceedings of the second cycle and space weather euroconference
2nd Euroconference on Solar Cycle and Space Weather, SEP 24-29, 2001, VICO EQUENSE, ITALY
477(2002), p. 563-566
University of Antwerp
We calculated the area of polar zones of the Sun, A(pz), occupied by unipolar magnetic field on H,, synoptic magnetic charts, following Makarov (1994), from 1878 to 2000. We found a gradual decrease of the annual latitude of the high-latitude zone boundaries of the global magnetic field of the Sun at the minimum of activity, Theta(2m), from 53degrees in 1878 down to 38degrees in 1996, yielding an average decrease of 1.2degrees per cycle. We found that the area of polar zones of the Sun A(pz) has risen by a factor of 2 during 1878-2000. The area of the unipolar magnetic field at high-latitudes A, may be used as a new index of magnetic activity of the Sun. We compared Apz with the geomagnetic index < aa > and Wolf number W(t). A temperature difference of about 1.3degrees between the Maunder Minimum and the present time was deduced. We have found that the highest latitude of tile polar zone boundaries of the large-scale magnetic field during very low solar activity reaches about 60degrees. It is supposed that the Theta(2m) - latitude coincides with the latitude where partial derivative(r)w = 0, with w (r, sigma) being the angular frequency of the solar rotation. Tile causes of the waxing and waning of the Sun's activity in conditions like Maunder Minimum are discussed.