Giant particle accelerators in the sky

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Earth’s magnetic field traps high-energy particles. When the first satellites were launched into space, scientists led by James Van Allen unexpectedly discovered high-energy particle radiation fields, later named its explorers: the Van Allen radiation belt. Visualized, these look like two donut-shaped areas that encompass the planet.

Now, a new study led by researchers from the GFZ German Research Center for GFZciences suggests that electrons in the radiation belt can be accelerated to very high speeds locally. The study shows that the magnetosphere acts as a very efficient particle accelerator, which accelerates electrons to so-called hyper-relativistic energies. The study is published by Hayley Allison, a postdoctoral scholar at GFZ Potsdam, and Yuri Schpritz from GFZ and professor at the University of Potsdam Nature communication.

In order to better understand the origins of the Van Allen Belts, in 2012, NASA launched the Van Allen Probes Twin spacecraft to traverse this most harsh environment and make detailed measurements in this dangerous area. The measurements included a full range of particles moving at different speeds and in different directions and plasma waves. Plasma waves are similar to the waves we see on the surface of water, but are invisible to the naked eye. They can be compared to waves in electric and magnetic fields.

Recent observations have shown that the energy of electrons in the belt can go up to the so-called hyper-relative energy. These electrons with temperatures above 100 billion degrees Fahrenheit move so fast that their energy of motion is much higher than their energy given by Einstein’s famous formula E = mc2. They are so fast that the time for these particles slows down considerably.

Scientists were surprised to find these hyper-relativistic electrons and assumed that such high energies could only be reached by a combination of two processes: the inward transport of particles from the outer regions of the magnetosphere, which accelerates them, And a local acceleration of particles by plasma waves.

However, new studies show that electrons carry such incredible energies with plasma waves locally in the heart of the belt. This process is highly efficient. The unexpected discovery of acceleration of particles of hyper-relativistic energies in near-Earth space can help scientists understand the fundamental processes of acceleration on the Sun, near outer planets, and even in distant corners of the universe, where space Investigation does not occur.

Detecting a killer electron hot spot in Earth’s Van Allen radiation belt

more information:
Hayley Allison, Yuri Shripits: “Local Heating of Radiation Belt Electrons for High-Relative Energy” Nature communication, DOI: 10.1038 / s41467-020-18053-z

Provided by the Helmholtz Association of German Research Centers

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