October 30, 2009 Huntsville, Alabama - For twelve years, NASA has had a satellite positioned a million miles in front of Earth with the sun about 92 million miles beyond. Its mission has been to study particles that come near Earth from our sun, the solar system and the galaxy. The satellite is called Advanced Composition Explorer, or ACE, and some of the highly energetic particles ACE has been monitoring are cosmic rays.
The number of cosmic rays reaching Earth are lower when the sun is active and has a strong, turbulent magnetic field that interferes with cosmic ray travel. But when the sun is not active, more cosmic rays reach Earth. The sun is supposed to be in an increasingly active period of Solar Cycle 24 with a solar maximum originally expected in 2011 to 2012. But the sun has been abnormally quiet. Scientists have not seen such a persistently low sunspot number for at least a century. Further, the magnetic field of the sun is at the lowest strength measured in at least 50 years.