Sunspot

Dark areas on the Sun created by strong magnetic fields beneath the Sun’s surface. Sunspots appear dark because they are cooler than the surrounding areas of the photosphere. They range in size from 2,400 km (1,500 mi) to several times Earth’s size. Sunspots usually occur in pairs or groups of opposite magnetic polarity that rotate with the surface of the Sun. They are the footprints of magnetic loops pushing through the surface and holding plasma below. Manifesting intense magnetic activity, sunspots host secondary phenomena such as coronal loops and reconnection events. Most solar flares and coronal mass ejections originate in magnetically active regions around visible sunspot groupings. Similar phenomena indirectly observed on stars are commonly called starspots and both light and dark spots have been measured.

A dark, fringed blemish on the solar surface caused by a concentration of the Sun's magnetic field. Sunspots look dark because they are cooler than the plasma surrounding them. Sunspots appear in groups and last from several hours to several months. The number of Sunspots increases and decreases over an eleven-year cycle called the solar cycle. Some individual spots cover areas 20 times the diameter of Earth.

In solar-terrestrial terms, an area seen as a dark spot on the photosphere of the sun. Sunspots are concentrations of magnetic flux, typically occurring in bipolar clusters or groups. They appear dark because they are cooler than the surrounding photosphere.

In the photosphere, i.e., visible disk of the Sun, a dark marking that manifests a magnetic anomaly that is associated with interference with radio communications on Earth. Note: Sunspot activity, i.e., the number of sunspots occurring at a given time or on a given day, is cyclic. The period of a cycle, from maximum through minimum and back to maximum sunspot count, is approximately 11 years.