Rare Northern Lights Light Up Utah — Another Display Likely as Large CME Heads Toward Earth

Rare Aurora Display Graces Utah; More Possible Wednesday

Massive eruptions of solar plasma produced a rare opportunity Tuesday evening to see the Northern Lights across much of the continental United States, including broad areas of Utah. Meteorologists say people who missed the multicolored Aurora Borealis might get another chance: continued coronal mass ejections (CMEs) could deliver another display on Wednesday.

What are CMEs?

Coronal mass ejections are enormous bubbles of hot coronal plasma threaded with intense magnetic field lines that the Sun expels over several hours, according to NASA. These structures often resemble huge, twisted ropes that scientists call "flux ropes." Fast CMEs can reach Earth in roughly 15 to 18 hours, although travel times vary widely depending on speed.

How CMEs affect Earth

When a CME reaches Earth, a strong transfer of energy from the solar wind into Earth's space environment can disturb the planet's magnetosphere. Those disturbances arise from changes in the solar wind that alter currents, plasmas and magnetic fields around Earth, producing geomagnetic storms and the aurora.

Two CMEs arrived Tuesday, sparking the geomagnetic storms that made the Aurora Borealis visible across much of the U.S. Forecasters say a third CME — and the largest of the three — is expected to arrive around midday Wednesday.

Shawn Dahl, service coordinator at the NOAA Space Weather Prediction Center, posted on X that the incoming CME is the most energetic of the recent activity: "That was the most energetic and strongest of this activity out there in space. It was traveling significantly faster than these other two, and we think that's going to pack even a stronger punch than what we've already experienced."

Storm strength and risks

NOAA uses a five-tier space weather scale to classify geomagnetic storms. While auroras are the most visible and celebrated effect, powerful geomagnetic storms can also interfere with critical systems on Earth — including power grids, air-traffic-control radio communications, and radio and GPS navigation.

Tuesday's storms reached G4 on NOAA's scale; forecasters currently expect the Wednesday arrival to produce approximately a G3 event.

Viewing tips for Utah

Some cloud cover is expected over parts of Utah on Wednesday. If skies clear, the best window to watch for renewed auroral activity is between sunset and midnight. To improve your chances, move away from city lights, check local cloud cover and follow real-time space weather updates from NOAA or the Space Weather Prediction Center.

Why auroras show different colors

The colors of an aurora depend on which atmospheric gases charged particles strike and the altitude of those collisions. The Canadian Space Agency summarizes the common colors:

• Green: The most common color seen from the ground, produced when charged particles collide with oxygen molecules at altitudes of about 60 to 120 miles.
• Pink and dark red: The lower edge of an aurora can sometimes show a pink or dark red fringe, caused by nitrogen molecules at roughly 60 miles altitude.
• Red: Higher in the atmosphere (about 120 to 250 miles), collisions with oxygen atoms can produce red auroras.
• Blue and purple: Hydrogen and helium can create blue and purple auroras, though those hues are often faint and harder for the human eye to distinguish against the night sky.

Note: While auroras are beautiful and photogenic, strong geomagnetic storms merit attention from utilities, transport and communications operators because of potential disruption to infrastructure.