Magnificent light pillars
From the ground north of Fairbanks, columns extended upward from city lights, reaching hundreds of feet into the air. The shafts of light resembled those accompanying popular monuments and memorials, luminous pillars piercing into the overcast night sky.
The phenomenon, known as light pillars, is very rare at the lower latitudes and occurs infrequently even in the Arctic. Light pillar development requires the perfect combination of temperature, moisture and wind.
At sufficiently low temperatures, trace amounts of moisture in the air freezes as hexagon-shaped ice crystals. What is known as diamond dust requires there to be nuclei, or small particulates in the air, for ice crystals to form around when temperatures are above 10 or 15 degrees.
In the case of Friday morning, it’s likely that the presence of diamond dust in the air was enhanced by the ashy soot and aerosols originating from vehicle traffic and industry in Fairbanks.
Each of the small ice crystals acts as a mirror, such that light shining on from the ground up into the sky is reflected back toward the surface in the direction of an observer. Ice crystals at different heights bounce back different beams of light, allowing a vertical column of luminance to form over natural light sources or those of human origin.
There were also patches of light to moderate snow falling at the time beneath a mostly clear sky, courtesy of moisture trapped beneath a low-level inversion, or an uptick in temperature with height.
In the photos I snapped, it’s even possible to see some of the individual crystals of diamond dust glinting in the light. I was amazed to see even the headlights of approaching cars on the northbound side of the Steese Highway generating their own towering columns of light.
While I was photographing light pillars adjacent to a U-Haul storage facility, I noticed a band of aurora becoming increasingly bright overhead. The colors weren’t overly vibrant yet, but I bet on its appearance signifying a more dramatic show to come. I decided to drive west of Fairbanks to escape terrain-induced snow showers in the Tanana Valley.
Much like my friend and I had done earlier in the week, we set up shop in the town of Ester, about 20 minutes west of Fairbanks, where we took advantage of clear skies brightened only by the aurora and a waxing crescent moon. The show was fun to watch, but it paled in comparison with what would arrive just 20 hours later.
On Friday night, a spurt of swiftly moving solar wind hit Earth’s magnetic field, or magnetosphere. The solar wind, which carries high-energy particles from the surface of the sun outward into space, can interact with the magnetosphere to induce epic displays of the northern and southern lights. The aurora are even more prominent around the time of the equinox thanks to something called the Russell-McPherron effect.
By midnight Friday, a full-fledged geomagnetic storm was ongoing; glimpses of the aurora borealis dipped all the way into the northern tier of the Lower 48, and shined brightly over Alberta, Manitoba and Saskatchewan. A NOAA satellite called Suomi NPP captured the display from above using its day/night band, sensitive to emissions of light produce by the aurora.
I had planned my return flight from Alaska to maximize my chances of flying beneath the aurora, which coincided perfectly with the solar storm. Because the flight passed directly beneath the auroral oval, which had swollen south thanks to the arrival of an enhanced solar wind, I wasn’t just witnessing an emerald glow on the horizon — the aurora was dancing directly overhead.
It appeared as bright columns of light delivering pinpricks to the sky overhead while simultaneously rippling like laundry strung out in the wind. Occasional eddies of glowing plasma swirled through the sky, the display unlike any of the comparatively meager shows I had witnessed in days prior.
The intensity of the geomagnetic storm surprised even forecasters at the Space Weather Prediction Center in Boulder, Colo., who had called for a G1 storm. Geomagnetic storms are ranked on a 1-to-5 scale. Friday’s episode was a G2 event.
The most dramatic display lasted only 15 minutes but produced a sight beyond words. The climate and weather of Alaska are unique, elegant and capricious — but above all beautiful.