Aurora, meet Airglow

Two of Earth’s most colorful upper atmospheric phenomena, the aurora and the glow of the air, met just before dawn in this photo taken by an astronaut on the International Space Station (ISS). Wavy green strands topped with red northern Lights appear to cross the band of faded red-yellow light as the ISS passed just south of the Alaska Peninsula. The rising sun behind the terrestrial branch at the time of this photo adds a deep blue to the horizon. City light from British Columbia and Alberta, Canada joins starlight to dot the morning sky.

Although they appear at similar altitudes, auroras and air glow are produced by different physical processes. The nighttime glow (or nightlight) is a type of chemiluminescence – the emission of light from chemical interactions between oxygen, nitrogen, and other molecules in the upper atmosphere. Airglow happens everywhere on Earth, all the time. However, the “night glow” is much easier to spot on a dark Earth than the “daylight” because the glow in the air is only a billionth more than the Sun.

The Northern Lights, on the other hand, come from interactions between solar energy and the Earth’s magnetic field. The magnetic field carries energy into the upper atmosphere, where it interacts with the same atoms as the airglow (mainly oxygen and nitrogen). This is why the two phenomena can produce similar colors. The dynamic nature of Earth’s magnetic field moves solar energy irregularly, making each aurora event visually unique.

Recently, the Earth Sciences and Remote Sensing Unit at NASA’s Johnson Space Center used machine learning to identify all the photos astronauts have taken of aurora over the past decades. Search the Gateway to Astronaut Photograph of Earth for “Aurora” to view over 270,000 photos of these magnetic wonders.

Astronaut photograph ISS062-E-98264 was acquired on March 16, 2020 with a Nikon D5 digital camera using a 50-millimeter lens and is provided by the Earth Observation Team of the crew of the ISS and the Earth Sciences and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 62 crew. The image has been cropped and enhanced for contrast, and lens artifacts have been removed. The International Space Station program is supporting the laboratory as part of the ISS National Laboratory to help astronauts take and render photos of the Earth that will be of greatest value to scientists and the public. available for free on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA / JSC Gateway to Astronaut Photography of Earth. Caption by Alex Stoken, Jacobs, JETS contract with NASA-JSC.