Watch for Northern Lights Following Strong Solar Flares
July 05, 2012; 7:11 PM
Strong solar flares have been occurring, bringing the potential for a northern lights show to the northern tier of the U.S.
There were at least three solar flares so far on Wednesday. They were classified around the middle M-class. The strongest one so far, classified as an M5.3, is considered to be a strong, significant solar flare. The highest classifications are called X-class solar flares.
AccuWeather.com Astronomy blogger Mark Paquette compared the strength of a solar flare to the Richter scale. Number classifications for a solar flare increase exponentially in strength.
This photo of the northern lights was captured in Beavercreek, Ohio, which is located east of Dayton, at 9:30 p.m. on Oct. 24, 2011. It was submitted by AccuWeather.com Facebook Fan Joseph L.
The strength of a solar flare alone is not enough to determine whether there could be a northern lights display for portions of the U.S. A solar flare must produce a coronal mass ejection, or CME, which is a mass of energy expelled from the sun's surface.
"It depends on the duration of the event. How much of a spike. If we get a quick spike of a solar flare, those usually do not produce CME's," Hunter Outten explained.
Furthermore, a CME must be directed at the Earth, so that it compresses the interplanetary magnetic field southward to create an aurora.
The Sun unleashed a powerful solar flare on Nov. 4, 2003. The Extreme Ultraviolet Imager in the 195A emission line aboard the SOHO spacecraft captured the event. Photo from SOHO, ESA & NASA.
"One of the solar flares today did produce a CME. A satellite image showed that the CME will likely go south of the Earth, but we could get a glancing blow," Outten added.
Other than analyzing satellite information, looking at the strength of the solar wind and proton density can help indicate the strength a geomagnetic storm. The stronger the geomagnetic storm, the more likely viewers would be able to see the northern lights farther south than usual.
The most difficult part of forecasting whether a CME will have an impact on the Earth is the arrival time. However, Paquette said that a rule of thumb is it usually takes 36-48 hours to reach the Earth.
If a CME is directed at the Earth, avid skywatchers who live across the northern tier of the nation, from Washington state to the northern Plains, Upper Midwest and northern New England, may get a beautiful show from nature either Thursday night or Friday night.
The Northwest will be drying out with clearing skies, promoting great viewing conditions. Meanwhile, stormy weather and clouds could obstruct the view for some Midwesterners. Much of northern New England should be dry Thursday night; however, some showers and storms will be around Friday night.
Keep checking back for more details on AccuWeather.com.