A spectacular northern lights display might be seen Friday night in states as far south as New York and Idaho as a coronal mass ejection from the sun slams into our planet.
This plume of solar material was released from the same sunspot that unleashed a series of coronal mass ejections (CMEs) that triggered the "extreme" G5 geomagnetic storm on May 10, resulting in auroras being seen in all 50 U.S. states.
The upcoming solar storm is expected to be much less powerful, peaking at G1 or G2 strength. This storm could still lead to the northern lights stretching farther south than usual, with auroras possibly visible in northern states.
"A CME associated with the X1.4 flare, produced by Region 3697 earlier in the period, is likely to enhance the Earth's magnetic field late on 31 May into early on 01 Jun (UTC)," the National Oceanic and Atmospheric Administration's Space Weather Prediction Center said in a tweeted forecast on Thursday. "The aurora may become visible over some northern and upper Midwest states from New York to Idaho."
"Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine," the center said in a forecast on Friday, anticipating the storm being closer to a G1 strength.
The sunspot that released the CME heading toward the Earth is named AR3697 but was called AR3664 when it caused the May 10 solar storm. In the weeks since, the sunspot has traveled around the back of the sun as our star rotated and has shrunk down from the gargantuan 15-Earths-wide region it was before.
The sunspot also released an X-class solar flare at the same time as this newest CME, causing radio blackouts across the U.S. on Wednesday. Solar flares are bursts of X-ray and ultraviolet radiation traveling at the speed of light, while CMEs are clouds of solar plasma, which take a lot longer to reach the Earth.
When they slam into our magnetic field, CMEs trigger geomagnetic storms, which are measured on a scale of between G1 (minor) to G5 (extreme), with their strength depending on the power of the CME.
"The G rating roughly translates to the Kp 'planetary' index, which is a measure of how much the Earth's magnetic field is disturbed. How a CME actually perturbs the near-earth system is complicated and not so easy to predict," Sandra Chapman, an astrophysicist and director of the Center for Fusion, Space and Astrophysics at Britain's University of Warwick, told Newsweek.
More powerful storms are less common: There are about 200 G3 storms every 11-year solar cycle, with an average of 100 G4 storms and only about four G5 storms during this time. The May 10 geomagnetic storm was the first G5 storm since 2003.
Geomagnetic storms can lead to auroras because of the funneling of solar particles into our atmosphere by the magnetic field, usually close to the poles. These particles collide with atoms of oxygen and nitrogen in the atmosphere, causing them to glow in the spectacular colors characteristic of the northern and southern lights. Excited oxygen generally glows red and green, while nitrogen releases blue and purple light.
More powerful geomagnetic storms result in these solar particles entering the atmosphere farther away from the poles, meaning that the northern lights can be seen farther south than usual.
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