Chuck Bednar for redOrbit.com – @BednarChuck
In you live in the northern US and were up late last night, you were probably treated to one heck of a light show! After a long night of St. Patty’s partying, you might have thought that you just imagined the green streaks in the sky, but you didn’t! The lights were courtesy of a rare atmospheric event that helped make the aurora borealis visible as far south as Michigan, as well as in some parts of Europe and Asia.
Also known as the Northern Lights, the aurora is typically visible only in the Arctic, but the combination of a severe geomagnetic storm and clear skies in many parts of the world (including the upper Midwest, Ohio Valley, and parts of the Mid-Atlantic in the US and the northern part of the UK) brought the phenomenon to a far larger audience, according to Mashable.
Even the sun celebrates St. Patty’s Day
Geomagnetic storms are disturbances of Earth’s magnetosphere that take place when there is a highly efficient exchange of energy from the solar wind into the space environment surrounding the planet. These space weather events result from solar wind variations that produce significant changes in the currents, plasmas, and fields in Earth’s magnetosphere.
[STORY: The world’s best places to see auroras]
The solar wind conditions required to produce geomagnetic storms are sustained (lasting for at least several hours) period of high-speed solar wind, and more importantly, a southward-aimed solar wind magnetic field (opposite that of Earth’s) at the magnetosphere’s dayside. The enables the most effective energy-transfer from the solar wind into Earth’s magnetosphere.
Tuesday’s geomagnetic storm was likely caused by the combination of a pair of coronal mass ejections (CMEs) from an active sunspot region the Washington Post said. Models originally predicted just a “glancing blow” from the CMEs, but the disruptions wound up being far more intense than expected, they added.
Bob Rutledge, lead forecaster at the Space Weather Prediction Center, told reporters that the storm had reached its peak intensity as of early Tuesday afternoon, but that conditions could last for another 12 hours, after which time it would begin to decay. While the Center had received no reports of interference with satellite electronics and high-latitude flights, Rutledge said that there was a chance that some GPS and sat nav systems could be disrupted.
[STORY: NASA-funded sounding rocket to fly into heart of aurora]
Previous geomagnetic storms of this caliber (G4 intensity on a five-point scale) had resulted in reports of aurora sightings “as far south as Tennessee, New Mexico, and Oklahoma,” said Brent Gordon, the center’s branch chief. He added that “a lot of factors go into whether you can see the aurora, cloud cover most importantly, and proximity to city lights. We are favorable in terms of the moon being crescent, which will give us pretty dark skies.”
Mashable noted that there is “no precise way” to predict whether or not the Northern Lights will be visible in the south, but the center does provide a series of tracking aids on its website, such as the Planetary K-Index, which measures the magnitude of geomagnetic storms. Real-time maps of aurora likelihood and short-term forecast models are also available online.
[STORY: Christmas lights from space]
How do you know if the lights you saw in the sky actually was the aurora? In an article for Slate.com, meteorologist Eric Holthaus said that if it the Northern Lights aren’t all that active, they will appear as “a faint green glow just above the horizon” that can easily be confused with “light light pollution from a nearby city.”
“The key difference is the aurora will be gradually morphing over time. If you set up a long-duration exposure on your camera (at least 30 seconds), you may notice faint pillars of green emanating upwards from the horizon. That’s the aurora,” he explained.
Those who are more fortunate or live further north may see the aurora as “vertically oriented greenish-gray streaks in the sky,” Holthaus added. “If you’re really lucky, it’ll be obvious (and breathtaking) that what you’re seeing is the northern lights – the continuously changing pillars of greens (oxygen) and reds (neon) and purples (argon) are caused by high-energy particles from the sun tunneling into the Earth’s upper atmosphere.”
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