Sunspot

Sunspots are relatively cool regions of the Sun's photosphere(which, thus, appears dark), and are large enough to be visible to the naked eye. They are regions of high magnetic fields with a temperature of 4,000?°K, some 2,000?°K cooler than the surrounding area. They provide a visible indicator of the solar magnetic cycle, which peaks every eleven years. The solar magnetic field has been shown to affect radio reception on Earth, and also, to affect living organisms.