Last night a G4 (severe) solar storm produced visible aurora across the Valley; skies may allow another viewing tonight between about 8:00 p.m. and midnight if you look due north. The display was caused by a CME — a coronal mass ejection — sending charged particles that interact with Earth's magnetosphere. Colors reflect altitude and gases: red and green come from atomic oxygen at different heights, while blue and purple stem from molecular nitrogen and its ions. For best results, go to a dark location, let your eyes adjust, and consider using a tripod for photography.
Aurora Tonight: Why the Northern Lights Lit the Valley — and How to See Them Again
Last night a G4 (severe) solar storm produced visible aurora across the Valley; skies may allow another viewing tonight between about 8:00 p.m. and midnight if you look due north. The display was caused by a CME — a coronal mass ejection — sending charged particles that interact with Earth's magnetosphere. Colors reflect altitude and gases: red and green come from atomic oxygen at different heights, while blue and purple stem from molecular nitrogen and its ions. For best results, go to a dark location, let your eyes adjust, and consider using a tripod for photography.
10:03 PM, 11/12/2025Science
Aurora Alert: G4 Solar Storm Lights Up the Sky
Last night a G4-class (severe) solar storm produced visible aurora over the Valley, and many people were able to see and photograph the Aurora Borealis with the naked eye. If you missed it, you may get another chance tonight — face due north between about 8:00 p.m. and midnight for the best odds.
What caused the display?
The show was driven by a CME (coronal mass ejection): a large eruption of plasma and magnetic field from the Sun. When a CME reaches Earth, its charged particles interact with our planet's magnetosphere and are funneled along magnetic field lines into the upper atmosphere near the poles. There they collide with atmospheric gases and cause the glowing curtains of light we call the aurora.
What do the colors mean?
Red: Emitted by excited atomic oxygen high in the atmosphere (typically above ~200 km). The red 630.0 nm emission is most visible during strong solar activity because oxygen is less abundant at those higher altitudes.
Green: Produced by atomic oxygen at lower altitudes (around 100–150 km). The bright green 557.7 nm line is the most common auroral color seen from the ground.
Blue and purple/violet: Result from molecular nitrogen and ionized molecular nitrogen (N2 and N2+). These emissions tend to appear at lower altitudes and are often seen when incoming particles have higher energies.
Viewing tips
To improve your chances: find a dark spot away from city lights, let your eyes adapt for at least 15–30 minutes, and face north where the aurora is most likely to appear. If photographing, use a tripod, wide-angle lens, long exposure (several seconds), and a high ISO setting.
Note: G4 storms are classified as "severe" by NOAA and can affect power systems, satellites, and radio communications. Enjoy the aurora but be aware of potential space-weather impacts.