Why Has the Sun Gone So Quiet?

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Although the sun is our nearest star, we certainly don’t have it all figured out.

Take, for example, that last week or so — the sun’s disk has been mostly sunspot-free and the X-ray output of the sun has plummeted since the beginning of July. This is in stark contrast to all the fireworks in the first few months of 2014.

To make the whole matter even more confusing, the sun should be at its peak activity, but just one look at the various images from solar observatories show a quiescent, blank solar disk, save for one sunspot (as of July 22). What’s going on?

The best answer is: we don’t really know. However, that doesn’t come as a surprise to many solar scientists.

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“It is weird, but it’s not super weird,” Tony Phillips, NASA solar physicist and author of SpaceWeather.com, told the LA Times. “To have a spotless day during solar maximum is odd, but then again, this solar maximum we are in has been very wimpy.”

The sun experiences 11-year cycles of activity. At its peak — known as “solar maximum” — the sun becomes a broiling mess of magnetism; huge arcs of magnetized plasma erupt from the surface, creating intense active regions. These regions peel back the hot chromosphere and photosphere (at the base of the sun’s multimillion degree corona), exposing the cooler plasma below. The contrast in temperature creates dark spots across the surface known as sunspots. The active regions are often the triggering points for explosive events like coronal mass ejections and solar flares — events that can impact Earth in subtle and not-so-subtle ways.

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It is for this reason that solar astronomers count the number of sunspots to gauge how active the sun is. And at present, the sun ain’t that active. In fact, space weather forecasters give a mere 1 percent chance that the sun will kick off a powerful X-class flare any time soon.

If the sun undergoes fairly predictable cycles of activity, why haven’t we figured out why sometimes the sun just seems to run out of steam? According to C. Alex Young, solar physicist at NASA’s Goddard Space Flight Center, Md., it’s not necessarily something strange, we just haven’t been observing the sun for long enough.

“We’ve only been observing the sun in lots of detail in the last 50 years,” Young said. “That’s not that long considering it’s been around for 4.5 billion years.”

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So although we know this is the weakest solar cycle on record, we may just be seeing part of a longer-term cycle that we haven’t been able to recognize as we haven’t been taking detailed notes of solar activity for long enough.

“It all underlines that solar physicists really don’t know what the heck is happening on the sun,” added Phillips. “We just don’t know how to predict the sun, that is the take away message of this event.”

While this is a curious phenomena, the lack of solar activity won’t impact our daily lives. However, satellite operators will probably welcome a less explosive stellar neighbor.

Sources: LA Times, Spaceweather.com

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