NASA (Photo credit: Wikipedia)
WAITING for solar fireworks to reach a grand finale next year? Um, sorry, looks like you already missed them. Structures in the sun's corona indicate that the peak in our star's latest cycle of activity has been and gone, at least in its northern hemisphere.
The southern hemisphere, meanwhile, is on a sluggish rise to solar maximum and may not hit its peak until 2014.
This bizarre asymmetry strengthens a theory that has been bubbling among sun watchers for the past few years: our star is headed for hibernation. Having the sun's outbursts turned off for a while would provide a better baseline for studying how they influence Earth's climate.
Observations of magnetic footprints called sunspots revealed in the 1800s that the sun moves through a roughly 11-year cycle of activity. Around a solar maximum, the star ramps up production of sunspots, flares and ejections of plasma. During a solar minimum, things quieten down.
Following an unexpectedly deep minimum from 2008 to 2010, solar physicists predicted a weak maximum for 2013. These days, though, sunspots aren't the only tools for charting the solar cycle. Richard Altrock of the US Air Force Research Laboratory in New Mexico has been studying coronal structures called polar crown prominences, which stem from magnetic rumblings on the sun's surface.
These gaseous filaments form at mid-latitudes at the beginning of a solar cycle. As it progresses they drift polewards, and when they reach 76 degrees latitude, a solar maximum has arrived. Soon afterwards the prominences disappear, only to form again during the next cycle.