Topline
The Northern Lights may be visible in the U.S. this weekend and into next week when a cloud of charged particles from the sun arrives at Earth just as our planet’s magnetic field is at its weakest. Space weather forecasters are warning of a “very strong” G3-class geomagnetic storm this weekend, with Sunday the night aurora could potentially be seen in northern skies from as many as 21 U.S. states as far south as Nebraska and Indiana.
Key Facts
The latest forecasts have a “strong” G3 geomagnetic storm striking on Sunday, March 23, a minor G1 geomagnetic storm on Monday, March 24, and a moderate G2 geomagnetic storm on Tuesday, March 25.
“A fast CME that left the sun on March 21 is expected to arrive at Earth by early on March 23,” said a statement from NOAA, referring to the effects of a coronal mass ejection — a dense cloud of charged particles that left the sun on March 21 and looks set to interact with Earth’s magnetic field.
According to NOAA, G3 storms can be seen from as low as Illinois and Oregon. It’s predicted to be as intense at Kp 7, which means “bright and active” aurora. Although unusual, it’s likely not going to be as strong as May 10, 2024’s extreme G5 geomagnetic storm, the most powerful for two decades.
NOAA’s aurora viewline has many as 21 U.S. states potentially see the Northern Lights on Sunday during the geomagnetic storm. They include Washington, Oregon, Idaho, Montana, Wyoming, North Dakota, South Dakota, Nebraska, Minnesota, Iowa, Wisconsin, Illinois, Indiana, Michigan, Ohio, Pennsylvania, New York, Massachusetts, New Hampshire, Vermont and Maine. U.S. states closest to the border with Canada will have the highest possibility of seeing the aurora.
With a last quarter moon on Saturday, there will be no moonlight in the evening sky during the potential show, which will make it easier to see, though the best views will be had in dark skies away from city lights. A mostly clear sky is also essential.
What’s Causing The Aurora This Weekend
After a few quiet weeks on the sun, it’s woken up with several small solar flares — bursts of electromagnetic radiation from the sun that travel at light speed. In the wake of an M1-class solar flare wake, a CME left the sun after an “eruptive event” from sunspot region 4028. Crucially, 4028 was in the center of the sun’s disk at the time, meaning the CME it produced is Earth-directed. However, CMEs take a few days to reach Earth. It’s a CME’s effect on the solar wind and Earth’s magnetic field that causes a geomagnetic storm and strong aurora.
Why This Week’s Equinox Is Critical
A CME created by an M-class solar flare wouldn’t normally be anything to get excited about. However, Thursday’s equinox makes a major display of aurora more likely. “It’s a faint and wimpy-looking CME, and normally wouldn’t cause a strong storm,” reports Spaceweather.com. “However, the Russell-McPherron effect boosts the effectiveness of CMEs around the equinox.” The Russell-McPherron effect is named after two scientists who investigated why aurora are twice as likely around the equinoxes. They concluded that cracks open in Earth’s magnetic field when the magnetic fields of Earth and the solar wind align, with solar wind entering to cause geomagnetic storms when normally they would not.
Key Background
Aurora is typically seen from the auroral oval in polar regions at around latitudes of 65-70 degrees north and south, but during strong geomagnetic storms, that oval can bulge, with displays then seen as far as 40 degrees north and south. That’s happening more frequently because the sun is currently at solar maximum, the peak of its 11-year cycle during which its magnetic activity waxes and wanes.
