The ancient Greeks believed the Sun to be perfect. All astronomical bodies were in the realm of the gods and, therefore, believed to be unchanging and unblemished. The detection of sunspots on the Sun's surface destroyed this belief and opened up a fascinating new view of our Sun as both dynamic and volatile.

The Sun is active in many ways. The Sun has long-term variations such as the solar cycle with a peak of activity every eleven years. On shorter timescales, we see that the Sun also rotates/spins. Sunspots and active regions appear around the Sun's eastern edge and disappear behind its western edge as the Sun rotates. We discussed solar rotation and solar cycles on Monday. Today we would like to concentrate on the short-term, or transient, changes which make the Sun so exciting.

Throughout the whole solar cycle -but most notably during times when the number of sunspots peak-the Sun creates major solar disturbances, or storms, which can have a significant effect on the Earth. These solar flares and coronal mass ejections occur relatively rapidly, causing the Sun to shine brighter across the whole electromagnetic spectrum. Charged particles of immense energies are produced and are, on occasion, sent hurtling towards the Earth!

Links:

Space Weather Introduction
More on Space Weather
Solar Flares
Coronal Mass Ejections
Auroras
P.O.E.T.R.Y. (Public Outreach, Education, Teaching and Reaching Youth)