A solar superstorm in May caused thousands of satellites to simultaneously maneuver to maintain altitude due to the thickening of the upper atmosphere, creating potential collision hazards as existing prediction systems struggled to cope. Space.com reports:

According to a pre-print paper published on the online repository arXiv on June 12, satellites and space debris objects in low Earth orbit – the region of space up to an altitude of 1,200 miles (2,000 kilometers) – were sinking toward the planet at the speed of 590 feet (180 meters) per day during the four-day storm. To make up for the loss of altitude, thousands of spacecraft began firing their thrusters at the same time to climb back up. That mass movement, the authors of the paper point out, could have led to dangerous situations because collision avoidance systems didn’t have time to calculate the satellites’ changing paths.

The solar storm that battered Earth from May 7 to 10 reached the intensity of G5, the highest level on the five-step scale used by the National Oceanic and Atmospheric Administration (NOAA) to assess the strength of solar storms. It was the strongest solar storm to hit Earth since 2003. The authors of the paper, however, pointed out that the environment around the planet has changed profoundly since that time. While only a few hundred satellites were orbiting Earth twenty years ago, there are thousands today. The authors of the paper put the number of “active payloads at [low Earth orbit]” at 10,000. […] The new paper points out that space weather forecasts ahead of the May storm failed to accurately predict the duration and intensity of the event, making satellite collision predictions nearly impossible.

On the upside, the storm helped to clear out some junk as defunct satellites and debris fragments spiraled deeper into the atmosphere. The authors of the report estimate that thousands of space debris objects lost several kilometers in altitude during the storm. More powerful solar storms can be expected in the coming months as the peak of the current solar cycle – the 11-year ebb and flow in the number of sunspots, solar flares and eruptions – is expected in late 2024 and early 2025.

The paper can be found here.