As we move closer to the peak of solar cycle 25, activity on the Sun is ratcheting up. One sign of that appeared in Earth’s atmosphere in the form of a dazzling display of the aurora borealis, or northern lights, that reached beyond the Arctic Circle deep into the midlatitudes.
In the early morning hours of February 27, 2023, the Visible Infrared Imaging Radiometer Suite (VIIRS) on the NOAA-NASA Suomi NPP satellite acquired this image of a ribbon of light in the skies over Quebec and Ontario. The nighttime satellite image was acquired with the VIIRS “day-night band,” which detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe signals such as airglow, auroras, city lights, and reflected moonlight.
A day later, NASA astronaut Josh Cassada took several photographs of the aurora (one of them below) from his perch on the International Space Station. The photo was taken while the International Space Station was passing over southeastern Manitoba. His comment on Twitter: “Absolutely unreal.” People on the ground reported spotting the pulsating reds, greens, and purples of the aurora in Alaska, Washington, Michigan, New York and as far south as Ohio, according to a report in The Washington Post.
A solar cycle is traditionally measured by the rise and fall in the number of sunspots, but it also coincides with increases in solar flares, coronal mass ejections (CMEs), radio emissions, and other forms of space weather. These bursts of magnetized plasma and energetic waves from the Sun’s atmosphere can energize the gases and particles in Earth’s magnetosphere. Those particles are sent crashing into Earth’s upper atmosphere at altitudes of 100 to 400 kilometers (60 to 250 miles), where they excite oxygen and nitrogen molecules and release photons. The results are rays, sheets, and curtains of dancing light in the sky.
According to the NOAA Space Weather Prediction Center, the Sun erupted with two CMEs on February 25 and 26, including one associated with an M6.2 solar flare. The biggest flares are known as “X-class” based on a classification system that divides solar flares according to their strength. The smallest ones are A-class (near background levels), followed by B, C, M and X. Similar to the Richter scale for earthquakes, each letter represents a 10-fold increase in energy output. In this case, geomagnetic storm activity reached G3 on a scale from G1 to G5.
If you like watching aurora displays such as this one, you can participate in aurora citizen science through a project called Aurorasaurus. The project tracks auroras around the world via reports to its website and on Twitter, then generates a real-time global map of those reports. Citizen scientists verify the tweets and reports, and each verified sighting serves as a valuable data point for scientists to analyze and incorporate into space weather models. The project is a public-private partnership with the New Mexico Consortium and is supported by the National Science Foundation and NASA.
Forecasts from space weather experts indicate the next peak of solar activity (solar maximum) will likely be reached in mid-2025.
NASA Earth Observatory image by Lauren Dauphin, using VIIRS day-night band data from the Suomi National Polar-orbiting Partnership. Astronaut photograph ISS068-E-59877 was acquired on February 28, 2023, with a Nikon D5 digital camera using an 24 millimeter lens and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 68 crew. The image has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Story by Adam Voiland.
