The surface of the Sun - Solar flares
Solar flares are caused by the magnetic field of the sun. The plasma is taken along the magnetic fieldlines.
On the movie you will see when you click the little camera to the
left you'll see the development of a number of solar flares. (1.1M Avi)
The energy liberated in an average solar flame is about equal to
10 billion French nuclear tests.
Two solar flares can be seen on these two short movies, made in 1995. The left
one is a 300k MPEG movie showing a flare on November 19, 1995. The right
movie is 169k and shows a flare on September 4. The show very clearly how
the flares are attached to the magnetic field lines.
At (b) in the figure to the left you can see a coronal hole,
from where particles can escape from the sun without being stopped by
the magnetic field. 
Such a `coronal hole' can be seen in the X-ray photograph to the right: The
dark area in the middle is a coronal hole.
These particles whizz by Earth about 5 days later,
with a speed of about 700 kilometers per second, or 1.5 million miles
per hour. They then cause aurorae or polar lights, cause
interference in radio reception, and mess up the navigation of birds.
More about that later...
