In a pre-print paper published on arXiv on June 12, researchers reported that during the intense four-day
solar storm
in May, satellites and
space debris
in
low Earth orbit
experienced a significant drop in altitude, sinking towards Earth at a rate of 590 feet (180 meters) per day. This sudden change in altitude forced thousands of
spacecraft
to simultaneously fire their thrusters to regain their original positions, according to Space.com.
The authors, William Parker and Richard Linares from the Massachusetts Institute of Technology highlighted the potential risks associated with this mass movement of satellites. They pointed out that collision avoidance systems may not have had sufficient time to calculate the rapidly changing paths of the satellites, potentially leading to dangerous situations.
The solar storm, which occurred from May 7 to 10, reached the highest level on the NOAA's five-step scale, classified as a G5 event. It was the most powerful solar storm to impact Earth since 2003. However, the authors emphasized that the space environment has undergone significant changes in the past two decades. While only a few hundred satellites orbited Earth twenty years ago, the number of "active payloads at [low Earth orbit]" has now reached approximately 10,000.
"The May 2024
geomagnetic storm
was the first major storm to occur during a new paradigm in low Earth orbit satellite operations dominated by commercial small satellites," the authors wrote.
Solar storms, caused by massive eruptions of charged gas from the sun, disrupt Earth's magnetic field and allow charged solar particles to penetrate deep into the atmosphere. These particles interact with air molecules, causing the spectacular northern and southern lights. However, they also heat up the atmosphere, causing it to expand.
As a result, the density of the sparse residual gases at satellite altitudes increases, causing satellites to lose altitude as they encounter increased drag from the thicker medium.
The study highlights the limitations of current space weather forecasting systems in accurately predicting the severity and length of the May solar storm, which made it nearly impossible to anticipate potential satellite collisions.
"The storm represented a serious challenge for the existing conjunction assessment infrastructure as it produced large, unpredictable perturbations on satellite trajectories in low Earth orbit," the authors wrote. "Automated station-keeping, especially from the Starlink constellation, caused nearly half of all the active satellites in [low Earth orbit] to manoeuvre at once in response to the storm. The combination of unpredictable satellite drag and bulk manoeuvring made it very difficult or impossible to identify potential conjunctions during the storm and in the days that followed."
Despite the challenges, the storm had a positive effect on
space debris removal
, as inactive satellites and debris fragments were pulled deeper into the atmosphere. The report's authors estimate that thousands of space debris objects experienced a decrease in altitude of several kilometres during the storm.
As the current solar cycle approaches its peak in late 2024 and early 2025, more intense solar storms are expected in the coming months. This 11-year cycle is characterised by fluctuations in the occurrence of sunspots, solar flares, and eruptions.
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