Light shed on sun’s stillness
Scientists have been puzzled over the last couple of years by the stillness of the sun – sunspots, flares and violent solar storms have been missing for much longer than is usual during the minimum period of the 11-year solar cycle. This week the US National Solar Observatory in Tucson, Arizona, said it had solved the mystery: a “jet stream” deep inside the sun is migrating more slowly than usual from the solar poles toward the equator.

The movement of this jet stream, flowing from east to west more than 1,000km beneath the solar surface, is a key component in the sun’s magnetic dynamo, which drives the 11-year cycle. When the jet stream reaches a critical latitude of 22º, the sun becomes more active again. This is happening now – putting paid to speculation that the solar cycle might have shut down altogether, as happened for several decades in the 17th century.