Call it a celestial tease.
Last weekend, the forecast spread rapidly on news sites and social media: Viewers as far south as Oregon and Maryland might catch a glimpse Thursday night of the storied northern lights thanks to a solar storm.
But it wasn’t to be. Forecasters now say the phenomena, also known as the aurora borealis, will be visible only at more typical — and far higher — latitudes.
Only the country’s northernmost states have a slight chance for aurora viewing, a semicircle that includes much of Montana, North Dakota and Minnesota and a slice of northern New England.
The aurora is a luminous, colorful glow often observed around the Earth’s North and South poles. It’s caused by streams of electrically charged particles traveling from the Sun to the Earth, called the solar wind.
Events on the Sun’s surface cause the ejections, which then collide with molecules in the Earth’s atmosphere, creating the brilliant light displays. The phenomenon is most often seen near the Earth’s two magnetic poles because the electrons from the Sun travel along the Earth’s magnetic field lines.
Predicting the aurora can prove challenging because it relies both on tracking conditions on the sun, and on predicting how the particles will interact with the Earth’s magnetic field, said Kevin Lewis, an associate professor in Johns Hopkins University’s Department of Earth and Planetary Sciences.
“I don’t know about you, but the last few days I keep seeing the rain forecast change about every hour,” Lewis said. “Predicting space weather carries the same uncertainty as well.”
In a statement, Don Hampton, a space physicist at the University of Alaska Fairbanks Geophysical Institute, said the university used information from the Space Weather Prediction Center, part of the National Oceanic and Atmospheric Administration, to make its original prediction, which has since changed.
“There are only a few satellites and instruments dedicated to collecting these data, so the models typically have a wide range of predictions since the observations are relatively sparse,” Hampton wrote. “While large solar storms can be seen leaving the vicinity of the sun, and their direction and speed can be estimated, once they leave the local solar vicinity they cannot be tracked. During this time the solar storms can be slightly diverted or even reduced, and the final impact on Earth’s magnetic field may be different than predicted.”
Bryan Brasher, a project manager for NOAA’s Center, said the original prediction for Thursday was prompted by the recurrence of a coronal hole, which caused elevated activity the last time it faced Earth.
“As this particular coronal hole rotated back into view — meaning we could see and analyze it — it was clear that it had diminished and we adjusted our forecast accordingly,” Brasher wrote in a statement.
Seemingly, the older forecast is the one that gained traction in media reports like that of the Associated Press, a wire service that disseminates stories to newspapers around the country.
But even that NOAA forecast wouldn’t have yielded an aurora display so far south, Brasher said. For that, you would need a strong or severe geomagnetic storm and NOAA had only predicted a moderate one.
The coronal hole, combined with a separate coronal ejection event that occurred July 9, could make faint aurora visible from U.S. states bordering Canada in the coming days — but nothing more, Brasher said.
Graphic on what causes the Northern Lights.TNS
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