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Jostled by a constant flow of charged particles from the solar wind, the Earth is not without its protection. Our planet is enveloped in a bubble of magnetism called the magnetosphere, spun from deep inside the planet.
As the solar wind blows, scientists have speculated that the edges of this bubble ripple in a series of energy waves in the plasma, generated by the interaction between the solar wind and the magnetosphere, along the direction in which the wind is blowing. But now they have discovered a surprise: some of the generated waves stop.
Space physicist Martin Archer of Imperial College London has been exploring the frontier of the Earth’s magnetosphere for several years.
“Understanding the limits of any system is a key problem,” he says. “This is how things come in: energy, momentum, matter.”
Recently, Archer and his colleagues discovered that the boundary of the magnetosphere, called the magnetopause, behaves like the membrane of a drum: strikes it with an impulse from the solar wind, and waves, called magnetosonic waves, propagate along from magnetopause to the poles. , and are reflected back to the source.
Now, using data from NASA’s Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, a team of researchers led by Archer has discovered that not only do these magnetosonic waves bounce back, but they can do so while traveling. against the direction of the solar wind.
So what happens when these waves meet the opposite wind? According to the modeling conducted by the researchers, the two forces can end in a dead end, the surge of the solar wind canceling the surge of the wave. A lot of energy is applied, but nothing is going anywhere.
“It’s similar to what happens if you try to go up an escalator down,” says Archer. “We’re going to make it look like you’re not moving at all, even if you’re trying a lot.”
Because these standing waves stay longer in the Earth’s magnetosphere, they could have a greater effect on particle acceleration, which in turn affects Earth. We know that plasma waves have an accelerating effect on electrons, which can “ride” plasma waves like a wakesurf uses water waves to accelerate.
The particles that accelerate along the magnetic field towards the poles are responsible for the beautiful auroras that light up our skies (as well as communication problems in the ionosphere).
Earth’s radiation belts, confined by the magnetosphere, could also be affected. Further research will be needed to understand the effects of these standing waves on particle acceleration.
Meanwhile, the researchers also translated the standing waves into sound. Archer and his colleagues have done this before, translating the sound of the drum-shaped responses of the magnetopause to the solar wind.
It’s not just a fascinating thing to experience; translating the spatial data into another medium can help scientists reveal information that we might otherwise have missed.
“While in a simulation we can see what’s going on everywhere, satellites can only measure these waves when they only give us time series and wavy lines. data can often give us a more intuitive idea of what’s going on, ”says Archer.
“You can hear the deep breathing sound of the permanent surface waves lingering throughout, increasing in volume with each pulse. The higher pitched sounds, associated with other types of waves, don’t last as long.”
The research was published in Nature Communication.
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