The sunspots are the most immediately visible features, when observing the Sun with appropriate filtration. They are well-defined surface areas that appear darker than their surroundings because of lower temperatures. They are regions of intense magnetic activity where convection is inhibited by strong magnetic fields, reducing energy transport from the hot interior to the surface. The magnetic field causes strong heating in the corona, forming active regions that are the source of intense solar flares and coronal mass ejections. The largest sunspots can be tens of thousands of kilometers across. The number of sunspots visible on the Sun is not constant, but varies over an 11-year cycle known as the solar cycle. At a typical solar minimum, few sunspots are visible, and occasionally none at all can be seen. As the sunspot cycle progresses, the number of sunspots increases and they move closer to the equator of the Sun.
31 мар 2010
