May’s solar superstorm, which lit up night skies around the world with colorful aurora displays, also triggered chaos in orbit as thousands of satellites had to maneuver simultaneously to maintain their altitude amid a sudden thickening of the upper atmosphere.
According to a preprinted document published on June 12 in the online repository arXiv, satellites and objects of space debris in low Earth orbit — the region of space up to an altitude of 2,000 kilometers — fell toward the planet at a rate of 590 feet (180 meters) per day during the four-day storm.
To compensate for the loss of altitude, thousands of spacecraft simultaneously began firing their thrusters to climb back up. The authors of the paper point out that this mass movement could have led to dangerous situations because collision avoidance systems did not have time to calculate the changing orbits of the satellites.
The solar storm that battered Earth from May 7 to 10 reached G5 intensity, the highest level on the five-point scale used by the National Oceanic and Atmospheric Administration (NOAA) to rate the strength of solar storms. It was the strongest solar storm to hit Earth since 2003.
However, the paper’s authors pointed out that the environment around the planet has changed profoundly since then. While only a few hundred satellites orbited the Earth twenty years ago, today there are thousands of them. The authors of the paper reported the number of “active payloads per [low Earth orbit]” for 10,000.
“The May 2024 geomagnetic storm was the first major storm to occur during the new paradigm in low-Earth orbit satellite operations dominated by commercial small satellites,” wrote study authors William Parker and Richard Linares of the Massachusetts Institute of Technology.
Solar storms, caused by massive eruptions of charged gas from the Sun, disrupt the Earth’s magnetic field. As a result, charged solar particles penetrate deep into Earth’s atmosphere, where they interact with air molecules. These interactions give rise to the amazing auroras and southern lights, but they also heat the atmosphere and make it bigger. As a result, the density of rare residual gases increases at the altitudes where satellites orbit. Satellites, suddenly faced with a much stronger environment, begin to lose altitude.
A new paper points out that space weather forecasts before the May storm failed to accurately predict the duration and intensity of the event, making predictions of satellite collisions nearly impossible.
“The storm posed a serious challenge to the existing conjunction assessment infrastructure because it caused large, unpredictable perturbations to the trajectories of low-Earth orbit satellites,” the authors wrote. “Automatic station keeping, especially from the Starlink constellation, caused nearly half of all active satellites in [low Earth orbit] to maneuver immediately in response to a storm. The combination of unpredictable satellite drag and mass maneuvering made it very difficult or impossible to identify potential conjunctions during the storm and in the following days.”
On the other hand, the storm helped clean up some junk as defunct satellites and pieces of debris spiraled deeper into the atmosphere. The report’s authors estimate that thousands of objects of space debris lost several kilometers in height during the storm.
Stronger solar storms can be expected in the coming months, as the peak of the current solar cycle—an 11-year ebb and flow in the number of sunspots, solar flares, and eruptions—is expected in late 2024 and early 2025.
Paper has been accepted for publication in the journal Spacecraft and Rockets.