Behold five and a half years worth of full-sun observations from XRT.
A dramatic illustration of the solar cycle, this movie
begins about one year before the first
sunspot ushered in the
current cycle on January 8, 2008.
The solar cycle is a periodic variation
in the Sun's activity that is caused by the gradual
"tangling" and eventual reversal of its magnetic field. Deep within the interior of
our star, a process known as a
produces the magnetic field, which
is then embedded in the Sun's plasma. Because the equatorial
regions rotate faster than the poles, the field slowly warps
until loops of magnetic field lines rise and protrude from the surface
here for a helpful animation). These protruding loops dramatically
change the structure of the Sun's corona, giving rise to energetic events
like flares and CMEs, and this is the change we see unfolding here. The movie ends less than a year from the
predicted peak of the coming solar maximum in early to mid 2013, after which the
polarity (positive and negative ends) of the Sun's magnetic field
will have reversed and the
number of active regions in the corona will begin to decrease again.