Satellites could face increased radiation risks after scientists identified that high-energy electrons breached a previously assumed impenetrable boundary. This boundary is part of Earth’s radiation belts, particularly known as the Van Allen belts.
A significant solar storm was responsible for breaching this boundary, allowing potentially harmful electrons to move at near-light speeds into areas they rarely reached before. This discovery followed a severe geomagnetic storm in May 2024, which pushed auroras unusually far from the poles. During and after the storm, the Japan Aerospace Exploration Agency’s Arase spacecraft noted a substantial presence of high-energy electrons closer to Earth than usual, according to research led by Nagoya University.
Understanding the Van Allen Radiation Belts
Earth’s magnetic field traps high-energy particles in two belt-like structures known as the Van Allen radiation belts. The outer belt predominantly contains high-energy electrons, whereas the inner belt contains mostly high-energy protons.
In 2014, scientists discovered a distinct boundary at the inner edge of the outer radiation belt, approximately three Earth radii from the planet’s center. One Earth radius equals about 6,371 kilometers, thus three radii stretch just over 19,100 kilometers. Historically, this boundary was known for stopping energetic electrons from crossing, earning the nickname of an “impenetrable wall.” However, the formation of this boundary is still not completely understood. A possible factor might be low-frequency radio waves called plasmaspheric hiss, which can expel energetic electrons from the radiation belts into the atmosphere.
The Impact of the May 2024 Solar Storm
During the May 2024 storm, Arase recorded a surge in electrons moving close to light speed inside the protected zone. Some electrons gained enough energy to penetrate certain satellite shields. This raised questions about whether these electrons were pushed inward from the outer belt or accelerated locally.
“One of the key questions was how these highly energetic electrons appeared inside the barrier,” said lead author Yoshizumi Miyoshi, a professor at Nagoya University’s Institute for Space-Earth Environmental Research.
Researchers observed that existing electrons within this area accelerated and gained more energy. Electromagnetic waves known as chorus waves likely facilitated this process by speeding up the electrons. These naturally occurring space waves boost electrons’ speed and energy.
The solar storm caused disruptions in the plasmasphere, a zone of cooler, charged particles surrounding Earth. The outer boundary of the plasmasphere shifted closer to Earth, reducing the density of charged particles around the radiation boundary. This allowed hotter electrons to penetrate inward and generate intensified chorus waves.
The disrupted conditions lasted longer than usual. Typically, charged particle levels recover within two days, but after the May storm, recovery took between 4.3 and 4.7 days for more than half of the pre-storm levels.
Implications of the Findings
The discovery does not indicate a breach of Earth’s protective magnetic field or ground-level risk to people. The “impenetrable barrier” refers to a specific boundary within Earth’s radiation belts.
The findings highlight that powerful solar storms can alter boundary conditions, leading to high-energy electron accumulation in areas previously considered unreachable. This has implications for satellites traversing these regions, as the electrons can damage spacecraft components and reduce the effectiveness of solar panels.
Understanding the behavior of energetic electrons during intense solar storms can enhance scientists’ capability to predict space weather hazards and assess risks to satellites and other spacecraft. “This discovery underscores the necessity to comprehend and forecast how energetic electrons behave under severe space weather,” Miyoshi stated. “This knowledge is crucial for evaluating radiation risks to spacecraft and improving space weather predictions.”
For further details, Newsweek reached out to Miyoshi. The article was produced with assistance from Martyn, Newsweek’s AI assistant. For more about Martyn, visit Newsweek’s website.
Contact editors for this story: Daniel Orton and Trevor Davies.
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