Earth's magnetosphere, the region of space dominated by Earth's magnetic field, protects our planet from the harsh
battering1 of the solar wind. Like a protective shield, the magnetosphere absorbs and
deflects2 plasma3 from the solar wind which originates from the Sun. When conditions are right, beautiful dancing
auroral4 displays are generated. But when the solar wind is most violent, extreme space weather storms can create intense radiation in the Van Allen belts and drive electrical currents which can damage terrestrial electrical power
grids5. Earth could then be at risk for up to trillions of dollars of damage. Announced today in Nature Physics, a new discovery led by researchers at the University of Alberta shows for the first time how the puzzling third Van Allen radiation belt is created by a "space
tsunami6." Intense so-called ultra-low frequency (ULF) plasma waves, which are excited on the scale of the whole magnetosphere, transport the outer part of the belt radiation harmlessly into interplanetary space and create the
previously7 unexplained feature of the third belt.
"
Remarkably8, we observed huge plasma waves," says Ian Mann, physics professor at the University of Alberta, lead author on the study and former Canada Research Chair in Space Physics. "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 research also points to the importance of these waves for reducing the space radiation threat to satellites during other space storms as well. "Space radiation poses a threat to the operation of the satellite
infrastructure9 upon which our twenty-first century
technological10 society relies," adds Mann. "Understanding how such radiation is
energized11 and lost is one of the biggest challenges for space research."
For the last 50 years, and since the accidental discovery of the Van Allen belts at the beginning of the space age, forecasting this space radiation has become essential to the operation of satellites and human exploration in space.
The Van Allen belts, named after their discoverer, are regions within the magnetosphere where high-energy protons and electrons are trapped by Earth's magnetic field. Known since 1958, these regions were historically classified into two inner and outer belts. However, in 2013, NASA's Van Allen Probes reported an unexplained third Van Allen belt that had not previously been observed. This third Van Allen belt lasted only a few weeks before it vanished, and its cause remained
inexplicable12.