OUR MAGNETIC SUN
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Often bigger than the Earth, sunspots form when particularly intense magnetic fields break through the Sun’s surface. Because the solar material is then held at bay by the magnetic field, the gas inside the Sun does not have to push outwards as hard, and so the area of the sunspot remains cooler and darker than its surroundings.
The number of sunspots grows and declines every 11 years. This solar cycle is related to changes in the Sun’s overall magnetic field, which reverses every 11 years. The magnetic north pole becomes the magnetic south pole, and vice versa.
In addition to sunspots, the Sun produces solar flares when its magnetic field lines become twisted like rubber bands until they reach breaking point and catapult matter into space. The biggest events, when huge quantities of matter and electromagnetic radiation are ejected, are known as coronal mass ejections (CME).
The Sun’s magnetic field is thought to be created by electrically charged currents of gas circulating in its interior. By rights, such a dynamo should run down, as it loses energy to its surroundings. However, a combination of solar rotation and hot matter convecting from below appears to keep the magnetic dynamo going.
A selection of amateur astrophographers’ images of sunspots (top row) and solar prominences (bottom row). Prominences maintain their loop form and remain anchored to the Sun while flares are eruptions that break free from the Sun and fling protons and...