In late November 2022, a minor geomagnetic storm in Earth’s magnetosphere led to a vibrant display of the aurora borealis, commonly known as the northern lights. The light show dipped south of the Arctic Circle, where it was especially bright over mainland Nunavut and Hudson Bay in northeastern Canada.
The light of the aurora is visible in this image, acquired around 2:30 a.m. local time (08:30 Universal Time) on November 29, 2022, by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the NOAA-NASA Suomi NPP satellite. VIIRS has a day-night band that detects nighttime light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe signals such as city lights, reflected moonlight, and auroras.
To human observers on the ground and in space, auroras appear as dynamic, colorful displays of light. The phenomenon occurs when fast-moving particles from space collide with oxygen and nitrogen molecules in Earth’s upper atmosphere and excites them. As the gases return to their normal state, they emit small bursts of energy in the form of light; oxygen molecules and atoms tend to glow green, white, or red, while nitrogen tends to be blue or purple.
On November 29, particles carried by solar wind that was moving almost 700 kilometers (430 miles) per second spurred the minor geomagnetic storm. The VIIRS sensor detected the light emissions as energetic particles rained down from Earth’s magnetosphere into the upper atmosphere. The light’s intensity is displayed in grayscale in the image above.
The solar wind streamed from an area of relatively cooler material in the solar atmosphere, known as a coronal hole. Coronal holes appear throughout the Sun’s solar cycle, which lasts an average of 11 years. But space weather events known to cause geomagnetic storms, such as solar flares, coronal mass ejections, and radio emissions, tend to increase with the approach of the cycle’s peak, or “solar maximum.” The next solar maximum is forecasted to occur around mid-2025.
NASA Earth Observatory image by Lauren Dauphin, using VIIRS day-night band data from the Suomi National Polar-orbiting Partnership. Story by Kathryn Hansen.