Earth's Third Van Allen Radiation Belt Made By A "Space Tsunami"

An illustration to explain the dynamics of the ultra-relativistic third Van Allen radiation belt. Andy Kale

Earth’s incredible magnetic field is not only useful when using a compass. It is there to protect us, and life on Earth would not be possible without it.

The magnetic field stops energetic particles and it traps them in large swarms around the planet in zones that we call Van Allen radiation belts. Two of these are well established and we now understand quite well how they behave, but in 2013 a third one was discovered.

According to a new study published in Nature Physics, the third belt is created by a space tsunami, large ultra-low frequency waves of plasma from the Sun, which allows particles to escape the outer belt and form a new structure in the magnetic field.  

"Remarkably, we observed huge plasma waves," said Ian Mann, physics professor at the University of Alberta, lead author of the study and former Canada Research Chair in Space Physics, in a statement.

"Rather like a space tsunami, they slosh the radiation belts around and very rapidly wash away the outer part of the belt, explaining the structure of the enigmatic third radiation belt."

The third Van Allen belt was only discovered three years ago when the Van Allen probes observed it for about four weeks before it was destroyed by a shockwave from the Sun. The probes are there to understand better how the magnetic field reacts to the complex interaction with the solar wind.

"Space radiation poses a threat to the operation of the satellite infrastructure upon which our twenty-first-century technological society relies," adds Mann. "Understanding how such radiation is energized and lost is one of the biggest challenges for space research."

Radiation in the belt can take the form of high-energy electrons, which are a significant threat to satellites, and to astronauts in space. Space weather can also have catastrophic consequences down on Earth. Large solar storms might cost the US alone somewhere between $1 to 2 trillion, and with a 1-in-8 chance that a megaflare will hit us by 2020, understanding Earth’s magnetosphere is paramount to keep us safe.


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