Sky watchers were caught off guard when a display of the Northern Lights made a surprise appearance in Oklahoma on March 24. Impressive pictures of the event continue to pop up all over the internet. Forecasters believe there is a small chance of more sightings in Oklahoma and other southern areas over the next few days.

Reports of other sightings from across the United States have also poured in from wherever skies were clear, reaching areas of Florida, Texas, New Mexico, Arizona, and California.

The Northern Lights (also known as Aurora Borealis) occur when magnetically charged particles that are ejected from the sun interact with Earth’s magnetic field, which serves as a shield to normally deflect slower moving particles. However, when the faster moving particles from an eruption strike, they plunge much deeper into the atmosphere where they collide with and excite atoms of nitrogen and oxygen. The energy from the collision creates vibrant light that ranges from green closer to the ground to red at higher altitudes.

The sightings in Oklahoma were all reported to be red. This is because the lights were farther north, so the green lights at the bottom were below the horizon due to the curvature of the earth.

The March 24 sightings that caught most space weather forecasters off guard were the result of a G4 solar storm. These storms are rated on a 1 to 5 scale, with 5 being the largest, so the G4 storm was fairly impressive, but not big enough to to make forecasters issue an alert for areas as far south as Oklahoma.

The Scientific America website explains that the storm was the result of a “coronal mass ejection” (CME), in which a large cloud of energetic and highly magnetized plasma erupts on the surface of the sun and is ejected out into space. This particular storm launched far slower than normal, so watchers had a harder time observing it.

Experts theorize the effects of the March 24 CME were amplified by a “coronal hole” they had observed earlier in the week. These holes are cooler, less dense regions of surrounding plasma, and allow solar wind to escape more readily into space.

A third contributing factor was the tilt of the earth at the time. Experts explain that during an equinox the earth’s magnetic field couples with the incoming magnetic particles in a way that is especially well suited for creating Northern Lights. The 2023 Spring equinox had occurred just three days earlier.

The combination of all three factors helps explain how experts were caught off guard by what they described as a “stealth event.” The result was an unusually large display of Northern Lights nobody was expecting.

Bob Leamon, a solar physicist at NASA’s Goddard Space Flight Center, explains that the activity on the sun works in an 11-year cycle, and this activity will continue to grow until it reaches its peak, called solar maximum, in 2025, when the sun’s magnetic field flips.

Leamon suggests that, as impressive as last week’s display was, he expects even larger events over the next couple of years.