A spot Free Sun still has a great influence on the Earth
Saturday, September 19, 2009
Although the Sun in recent years has had very few sunspots showing, nevertheless, there appears to have been a major influence on the earth. The solar researchers write in an article published today in Journal of Geophysical Research - Space Physics.
The number of sunspots is usually seen as a good indicator for the activity of the Sun, normally with an eleven-year cycle. The new cycle (cycle 24) shows unusually long time in the coming, nobody knows why.
With an armada of instruments on the ground and in space has now discovered that during the minimum of the protracted activity over recent years had very strong "winds" occurred in the solar wind - the stream of electrically charged particles from the sun into space is blown open. These solar wind flows were much more frequent and stronger in 2008 than in 1996, during the previous activity minimum.
The energy-rich solar wind flows, sometimes more than one week are sustained, have a major impact on the structure of the outer radiation belts of the earth, and indirectly on satellites in orbit. Apparently is the number of spots on the sun not good indicator of the overall Solar activity.
Why the solar wind flows last year were so frequent and powerful, is unclear. May be related to a progressive reduction of the magnetic field strength of the sun, resulting in the equatorial area being bigger "coronal holes"are created: openings in the rarefied solar atmosphere (the corona) which electrically charged particles at high speed can easily escape .
Govert Schilling (all about astronomy)