Deirdre Collins
Georgetown University
On August 5, Camp 18 echoed with rumors that the Northern Lights, or the Aurora Borealis, would make an appearance later that night. The clear and starry night sky enclosed us and appeared faintly green, exciting onlookers with fantasies of one of the Earth’s most impressive phenomena. Determined not to miss the twisting and twirling lights that would dance through the night, my friends and I decided to sleep on the north side of camp and set alarms every hour to inspect the sky. By half past midnight, my excitement had kept me up way past my normal bedtime. The sky glowed light green, indicating that the Aurora had started and foreshadowing the curtains of light that would soon appear above me. Constellations like the Big Dipper were sprinkled delicately across the vast expanse of space above. Without quite realizing it, I soon drifted off to sleep, hoping that my next conscious moments would be under the Aurora.
At 2 am, I was awoken by my friends who wore faces of pure wonderment and admiration. As my eyes adjusted to the light above me, I saw it — curtains of lime green light meandering and moving quickly through the sky. Streaks of violet and white radiated from the snaking luminance that occupied our astonished minds. The lights twisted and turned rapidly around each other and we tried not to blink for fear that we would miss a second of something so spectacular. Shooting stars cut through the Aurora every now and then, appearing to pierce through the light that moved so rapidly through the sky. Curled up in our sleeping bags under the show, we lay there contemplating the power and beauty of nature and as scientists, questioning the mechanisms that could produce such magnificence. The scientific understanding that underlay the beauty of the Aurora is what truly captivated me that night on the Camp 18 nunatak above the Juneau Icefield.
Storm Range at Camp 18 under the Aurora Borealis. Photo Credit: Deirdre Collins
The Aurora Borealis in the northern hemisphere, and the Aurora Australis in the southern hemisphere, result from solar storms. Large amounts of highly charged particles from the sun travel towards the Earth and interact with the Earth’s magnetic field. These charged particles travel along the Earth’s magnetic field to the planet’s north and south poles. Entering the Earth’s upper atmosphere, roughly 100-200 km above the surface, these highly charged particles excite various gases. When these gases return to a resting state — their electrons moving back down an orbital or energy level — releasing visible radiation (light!). According to the American Geophysical Union’s Earth & Space Science News, the Aurora is most prominent 2-3 days after outbursts of high solar activity. The type of gas and the difference in energy between the gas’s excited and resting states determine the wavelength of light released and, therefore, the color we see in the night sky. The greens and yellows we observe in the Aurora result from the release of radiation from one gas, whereas the purples we see result from release of radiation from another gas. The excitement of atmospheric gases by the interaction of highly charged particles from the sun with the Earth’s magnetic field produce one of the most spectacular wonders observed by man. It was both the exquisiteness of the Northern Lights and their intriguing scientific explanation that captivated me as I lay on a nunatak on the Icefield that night following the colorful lights as they danced throughout the sky.
Mountains above the Gilkey Trench under the Aurora Borealis. Photo Credit: Deirdre Collins