The total number of sunspots varies during the 11-year solar cycle, with the peak of sunspot activity coinciding with solar maximum and a sunspot hiatus coinciding with solar minimum, according to the Space Weather Prediction Center of the National Oceanic and Atmospheric Administration (NOAA). Sunspots are darker, cooler areas on the surface of the sun that arise due to disturbances in the sun's magnetic field. The last pole reversal happened about 780,000 years ago. In 2006 the sun ejected a small coronal mass ejection (CME) - a release of plasma and magnetic field - which hit Venus and stripped the planet's atmosphere of vast amounts of oxygen.Įarth's magnetic poles also flip, but the interval between the reversals is much longer, averaging about every 300,000 years according to NASA Climate. Planets without a protective magnetosphere such as Venus feel the full impact. When the sun's magnetic poles flip, the effects ripple through the solar system since the heliosphere - the region of space that is influenced by the solar wind - extends billions of miles or kilometers beyond Pluto according to the statement. This is a regular part of the solar cycle.'
'The sun's polar magnetic fields weaken, go to zero and then emerge again with the opposite polarity. In a NASA statement, solar physicist Phil Scherrer of Stanford University describes what happens during the solar cycle.
