Sunspots are dark splotches on the Sun caused by the appearance of cooler (4500oC) areas amidst the roiling gases on the surface (6000oC). These areas are cooler because much of their energy is tied up in intense magnetic fields. Physically sunspots are anomalies in the large-scale magnetic field of the Sun. Spots always appear in pairs, like a dipole magnet. The magnetic field strength in a sunspot may exceed the Earth's magnetic field intensity by a factor of 10,000.
Sunspots and the active area around them sometimes emit huge amounts of particles and electromagnetic radiation. Especially violent are the so-called flares, which eject enormous amounts of particles and radiation. If such bursts hit the Earth, magnetic observatories register large variations in the Earth's magnetic field and magnificent northern lights can be seen even at low latitudes. During such magnetic storms, electric currents are induced in power lines and gas pipelines, which may in some cases damage transformers and cause increased corrosion in pipelines. Typical lifetimes of sunspots vary from a couple of days to several months.
