2024 was a big year for the Sun. First, April saw a total solar eclipse, providing nearly four minutes of quiet total eclipse across the continental United States. It also gave sun observers the opportunity to observe the outer layers of the sun’s atmosphere, which are usually obscured.
Then, on May 10-11, the Northern Lights seemed to appear everywhere at once. Reports of night skies turning green, purple and pink have come in from North Texas, Arizona and even Alabama, Florida and Tennessee (almost all of the country). In places where the light was too dim to be seen with the naked eye, it was also visible in camera photos. On October 10-11, another powerful aurora show dazzled.
The Northern Lights extend very little south until now. May’s unusual light show was the result of the largest geomagnetic storm since 2003 reaching Earth’s atmosphere. Geomagnetic storms begin when the sun emits a bunch of high-energy ions and electrons called coronal mass ejections (CMEs) in the direction of Earth.
Earth’s protective geomagnetic field deflects most such explosions. However, during powerful events like the one in May, these energetic particles interact with the atmosphere’s magnetic fields and gases to create auroras. The sun also emits bright flashes of light called solar flares. (This can accompany a CME, but is a separate phenomenon. Solar flares travel at the speed of light and reach Earth in 8 minutes. CMEs take several days.)
In 1859, the Carrington Event, the most powerful geomagnetic storm in recent history, struck the Earth. Witnesses reported that the storm disrupted telegraph lines, set telegraphs on fire, and even shocked correspondents. Today, such an event can cause much more damage than a small fire or a few explosions. Geomagnetic storms can threaten communications satellites, navigation systems, power grids, and more. For example, on Halloween 2003, powerful storms destroyed satellites and disrupted GPS systems used by airlines, deep-sea drilling, and other applications.
Although the storm in May was not as powerful as the Carrington event, it was rated a G5, the most severe rating, by the National Oceanic and Atmospheric Administration (NOAA). While people were admiring the aurora, space weather scientists were heaving a sigh of relief.
“Even though there have been a lot of impacts, we don’t recognize that there are a lot of really bad impacts,” says Shawn Dahl, a space weather forecaster at NOAA’s Space Weather Prediction Center in Boulder, Colorado. “This was the most successfully mitigated severe space weather storm in history.”
We are better prepared than we were in the past, says Dahl. Scientists use satellites to track changes in the sun’s temperature and magnetometers around the world to look for fluctuations in the magnetic field. “We can predict many of these events up to three days in advance,” he says. Last May, NOAA issued a six-hour advance warning, giving grid operators time to prepare and airlines time to redirect flights to safer routes. In the future, he hopes to roll out more widespread warning systems, including using GPS to alert farmers during planting and spraying operations.
There is a lot to look forward to. In March 2025, NOAA plans to launch a satellite for solar weather prediction. And NASA announced in October that the sun reached its solar maximum for its 11-year cycle. Activity levels could last another year, which means more CMEs, more flares and more auroras to shine in Dallas.
Stay tuned.
