OUR MAG­NETIC SUN

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Sky at Night Magazine - - SUPERFLARE­S -

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...

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