The Weakest Solar Cycle in 100 Years

[Deano]

Scientists are struggling to explain the Sun’s bizarre recent behavior. Is it a fluke, or a sign of a deeper trend?
The Sun is acting weird. It typically puts on a pageant of magnetic activity every 11 years for aurora watchers and sungazers alike, but this time it overslept. When it finally woke up (a year late), it gave the weakest performance in 100 years.

What’s even weirder is that scientists, who aren’t usually shy about tossing hypotheses about, are at a loss for a good explanation. Three scientists, David Hathaway (NASA / Marshall Space Flight Center), Giuliana de Toma (High Altitude Observatory), and Matthew Penn (National Solar Observatory) presented possible explanations at this month’s meeting of the American Astronomical Society’s Solar Physics Division, but their results sparked a lively debate rather than a scientific consensus.

A well-behaved Sun flips its north and south magnetic poles every 11 years. A cycle starts when the field is weak and dipolar—basically, a giant bar magnet. But the Sun’s rotation is faster at its equator than at its poles, and this difference soon stretches the field lines like distended rubber bands around the solar surface. Frenetic activity ensues, with magnetic tangles producing sunspots, prominences, and sometimes flares and plasma explosions. All of that dies down when the Sun-wide magnetic field lines finally snap into simpler configurations, re-establishing the dipole field and beginning the next cycle.
Full story & pics at Sky & Telecope

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