Jimmy Westlake: Auroras return to the Yampa Valley
March 19, 2013
It's been a long time since the aurora borealis has been seen in the Yampa Valley. The last good one I can recall was in November 2004. While most folks were snug in their beds during the wee hours of St. Patrick's Day morning, a 1-billion-ton cloud of hot plasma, ejected from the sun Friday, slammed into the Earth's protective magnetic field and sparked a moderate geomagnetic storm, sending auroras as far south as northern Colorado.
We generally get to see auroras this far south of the Arctic Circle only a few times a decade, when the sun is near the peak of its 11-year sunspot cycle. During these times of "solar maximum," lots of sunspots, solar flares and coronal mass ejections (CMEs) can erupt on the sun before it quiets down for another decade.
When a solar eruption spews charged particles (mostly protons and electrons) into space, they can become entangled with the Earth's magnetic field and generate colorful, dancing lights in the upper atmosphere over the magnetic poles. Galileo, in the 17th century, coined the phrase "aurora borealis," or "northern dawn," to describe them.
The sun's 11-year heartbeat has been going strong for the last century, but the current cycle, known as Solar Cycle 24, has been a bit arrhythmic. After a much longer than usual solar minimum between 2008 and 2010, scientists predicted the next maximum might be the least active since 1906. Indeed, solar activity has remained very low during this year of the predicted peak. There was a small spike in activity in 2011, but the sun has been eerily quiet since then.
Even more puzzling is the lack of expected precursors for Solar Cycle 25. Some astronomers wonder if the sun's heartbeat is about to flat-line for some undetermined amount of time, as it inexplicably did for nearly a century during the 1600s. This prolonged period of solar calm, the so-called Maunder Minimum, coincided with an extremely frigid period in Europe known as the Little Ice Age.
So, it was with some degree of relief that I gazed at the mild display of the northern lights between the passing clouds St. Paddy's Day morning. Hopefully, the sun will continue to send auroras our way in the months ahead.
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For daily updates on all things astronomical, including aurora forecasts and warnings, visit the NASA-sponsored website http://www.spaceweather.com. You don't want to sleep through the next auroral storm.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. Check out Westlake's astrophotography website at http://www.jwestlake.com.
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