There is something new under the sun— or rather inside the sun. Usually our star follows a predictable pattern, becoming more and less active (as measured by flares, sunspots, and magnetic storms) on an 11-year cycle. But the most recent lull dragged on for 12.6 years. “You have to go back 99 years to find another minimum as long,” says Mausumi Dikpati, a physicist at the National Center for Atmospheric Research in Boulder, Colorado. Last August she announced an explanation.
Dikpati used computer simulations to model the gargantuan rivers of plasma that flow across the sun’s surface. Like Earth’s ocean currents, solar plasma normally rises at the equator and sinks at higher latitudes. During the recent solar minimum, however, plasma flowed all the way to the poles. Dikpati’s simulations show that these unusually long currents affect the magnetic fields near the surface, which indirectly determine the number of sunspots and the strength of solar flares. These findings may help astronomers predict solar storms, which can disrupt radio and satellite communications on Earth, and understand the underlying mechanism behind the sun’s 11-year heartbeat.