Airglow Displays Vibrant Green Streaks in the Colorado Sky, Hints Upcoming Solar Maximum

As a sign that the solar maximum is getting near, bright green streaks in the sky known as airglow persisted for two hours. It was captured on camera by a photographer in Colorado.

Airglow: Vibrant Green Streaks

In Colorado, close to the West Elk Mountains, Aaron Watson, a photographer, captured the breathtaking display. On June 21, just before midnight, streaky emerald lights appeared in the sky. They persisted for around two hours while gently moving across the sky. These lights have also been seen in other areas of Colorado, but in weaker form.

Watson initially thought the lights were noctilucent clouds, also known as night sparkling clouds, which were expected to be more common this year in the months of June and July. But as the vivid hues began to show, this seemed implausible. He also made the wild assumption that they might be a stationary auroral display, a similar phenomenon like STEVE or a steady auroral arc triggered by a solar storm slamming into Earth.

There was no solar storm at the time; instead, the lights are caused by a phenomenon called "airglow," which is brought on in the upper atmosphere of Earth by less intense sun radiation. Although airglow is infrequently seen from the ground, as solar activity increases, it may become more frequent in the upcoming months and years, Spaceweather.com said.

Solar Maximum

According to experts, the solar activity peak that was predicted to occur in 2025 and be relatively weak relative to prior peaks may possibly occur as early as the last quarter of 2023 and turn out to be more active than originally predicted. The observation of such vivid airglow adds credence to this theory.

The top of the roughly 11-year solar cycle, when solar activity is at its highest and the sun produces the most radiation and solar storms, is when airglow has traditionally been most apparent, according to a study published in March 2021 in the journal JGR Space Physics. According to NASA, monitoring changes in airglow can therefore aid in monitoring the development of the solar cycle. The frequency of auroras also increases at the solar maximum.

Solar energy that reaches Earth is what causes airglow and auroras, but they operate in different ways. Strong solar winds or coronal mass ejections that strike the Earth's magnetic field and briefly weaken it are what cause auroras. Due to the atmosphere's opening to solar radiation, vivid colors are created by the air molecules' excitation.

In contrast, airglow results from the daytime ionization of gas molecules by slow solar radiation. Ionized molecules interact with electron-rich gases at night, releasing energy as a slower and fainter light that resembles an aurora.

In the ionosphere, 50-300 miles above Earth, airglow can be seen. At greater altitudes, excited nitrogen atoms produce red colors, whereas excited oxygen atoms produce bright green lights around 56 to 62 miles in altitude, as per Spaceweather.com.

An impending solar maximum is also suggested by the warming of the thermosphere, which touches the ionosphere. This layer is rapidly warming and absorbing energy from recurrent solar storms, which is another sign of an approaching solar maximum, Live Science reports.