Fig6_3 Solar magnetic activity cycle

Fig6_3 Solar magnetic activity cycle

Fig. 6.3 . The 11-year solar cycle of magnetic activity plotted from 1975 to 2007. Both the positions of sunspots (top) and the numbers of sunspots (bottom) wax and wane in cycles that peak every 11 years. Similar 11-year cycles have been observed for more than a century. At the beginning of each cycle, the first sunspots appear at about 30 degrees solar latitude and then migrate to 0 degrees solar latitude, at the solar equator, when the cycle ends. This plot of the changing positions of sunspots resembles the wings of a butterfly, and has therefore been called the butterfly diagram. The cycles overlap with spots from a new cycle appearing at high latitudes when the spots from the old cycle persist in the equatorial regions. The solar latitude is the angular distance from the plane of the Sunís equator, which is very close to the plane of the Earthís orbit about the Sun, called the ecliptic. (Courtesy of David Hathaway/NASA/MSFC.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University