The sunspot cluster that illuminated the Chicago area’s sky with the aurora borealis three weeks ago will return this weekend, but the prospect of seeing the northern lights in the city this time remains hazy.
The National Oceanic and Atmospheric Administration predicts a moderate geomagnetic storm in the Northern Hemisphere late Friday night and early Saturday, causing the aurora borealis to stretch farther south than usual again, possibly just reaching the edge of northern Illinois.
The solar storm isn’t expected to create as flashy of a display as the aurora borealis seen across the Chicago area three weeks ago.
A category G2, or moderate activity, storm watch was issued for this weekend. In early May, NOAA issued a G4 watch for severe activity, but the storm resulted in G5 levels, or extreme activity, which is the top of the scale, according to NOAA.
“It’s not unusual for a sunspot cluster with the intense complexity of this one to maintain strength for weeks on end,” said NOAA Space Weather Prediction Center spokesperson Erica Cei. “The reason we’re seeing a return of activity now is because the sunspot cluster responsible for the early May activity has rotated back into Earth view. The sun’s rotation takes about 27 days.”
The Space Weather Prediction Center said the aurora borealis may be visible in northern Midwest states between Idaho and New York.
An aurora borealis forecast can be viewed at swpc.noaa.gov.
The northern lights, which are happening nearly constantly at both polar regions of the planet, are caused when coronal mass ejections of solar material from the sun reach Earth’s magnetic field, causing a geomagnetic storm. The neon lights are produced by collisions between the solar material and atoms and molecules of Earth’s upper atmosphere.
