The Sun That Did Not Roar
This is the height of the 11-year solar cycle, the so-called solar maximum. The face of the Sun should be pockmarked with sunspots, and cataclysmic explosions of X-rays and particles should be whizzing off every which way. Instead, the Sun has been tranquil, almost spotless.
On an otherwise blank solar disk, a single sunspot, dubbed AR1841, was the only visible activity in this Sept. 16 image
As W. Dean Pesnell, the project scientist for NASA’s Solar Dynamics Observatory, dryly noted, “We’re not having much of a solar maximum.”
A week ago, a solitary sunspot blemished an otherwise blank yellow disk. In the ensuing days, a few more specks appeared, but even a small explosion, or coronal mass ejection, last Thursday seemed like the halfhearted effort of a slacker star.
“The truth of it is there isn’t a lot going on,” said Joseph M. Kunches, a space scientist at the Space Weather Prediction Center. “It’s been a bit of a dud. You look at the Sun today and you say, ‘What?’ ”
For those who depend on Dr. Kunches’s work, like satellite operators and power companies, that is actually good news. One of the worries in our highly technological 21st-century civilization is that a direct hit on Earth by a gargantuan solar storm could disable satellites and overwhelm wide swaths of power grids. A quiet Sun makes that much less likely.
For scientists trying to understand the dynamics in the interior of the Sun, it has been a humbling experience enlightening them about how much they do not know. “If there’s anyone who has figured it out, I haven’t heard, that’s for sure,” said Douglas Biesecker, a physicist at the Space Weather Prediction Center and the chairman of a panel that had issued predictions about the solar cycle.
They do have a basic understanding. Inside the Sun, flows of electrons and protons generate magnetic fields that undulate on roughly an 11-year schedule. The roiling of the fields create regions that are cooler and darker — sunspots. The twisting magnetic fields within sunspots periodically snap, releasing enormous amounts of energy in solar flares and coronal mass ejections.
But some solar cycles are ferocious while others remain calm. Why the cycle is 11 years is another mystery.