PRB_Ohio writes: The sun is in the pits of a century-class solar minimum, and sunspots have been puzzlingly scarce for more than two years. Now, for the first time, solar physicists might understand why. The gist is that there is a 'jet stream' like phenomena about 7,000km below the surface of the sun. The streams migrate slowly from the poles to the equator and when a jet stream reaches the critical latitude of 22 degrees, new-cycle sunspots begin to appear. Scientists at the National Solar Observatory (NSO) in Tucson, Arizona, used a technique called helioseismology to track and analyze the streams.