We even had northern lights in Hawaii a few weeks ago, and it looks like they're coming back tonight. On Friday night, states as far south as New York and Idaho might see a spectacular northern lights display due to a coronal mass ejection from the sun. This solar material came from the same sunspot that caused the intense G5 geomagnetic storm on May 10, which made auroras visible in all 50 states. The upcoming storm is expected to be less powerful, peaking at G1 or G2 strength, but it could still make the northern lights visible in more southern states.
The National Oceanic and Atmospheric Administration's Space Weather Prediction Center tweeted on Thursday that a CME from the X1.4 flare produced by Region 3697 is likely to enhance Earth's magnetic field late on May 31 into early June 1 (UTC). They mentioned that the aurora might be visible in some northern and upper Midwest states, from New York to Idaho.
"The aurora may be visible at high latitudes, like northern Michigan and Maine," the Space Weather Prediction Center said on Friday, predicting the storm to be around G1 strength. The sunspot releasing the CME heading towards Earth is AR3697, previously called AR3664 when it caused the May 10 solar storm. Since then, it has rotated around the back of the sun and shrunk from its previous size of 15 Earths wide.
This sunspot also released an X-class solar flare at the same time as the latest CME, causing radio blackouts across the U.S. on Wednesday. Solar flares are bursts of X-ray and UV radiation traveling at the speed of light, while CMEs are clouds of solar plasma that take longer to reach Earth. When CMEs hit our magnetic field, they trigger geomagnetic storms measured from G1 (minor) to G5 (extreme), depending on the CME's power.
Sandra Chapman, an astrophysicist at the University of Warwick, explained that the G rating translates to the Kp 'planetary' index, indicating how much Earth's magnetic field is disturbed. Predicting a CME's effect on the near-Earth system is complex. More powerful storms are rarer, with about 200 G3 storms, 100 G4 storms, and only four G5 storms per 11-year solar cycle. The May 10 storm was the first G5 since 2003.
Geomagnetic storms can create auroras by funneling solar particles into our atmosphere, usually near the poles. These particles collide with oxygen and nitrogen atoms, causing them to glow in the northern and southern lights' spectacular colors: excited oxygen glows red and green, while nitrogen releases blue and purple light. More powerful storms can make the northern lights visible farther south than usual.