The terrestrial environment is two giant rings called the Van Allen radiation belts. These are powerful ions and electrons. Various processes can accelerate these particles to relativistic velocities that threaten the spacecraft. Therefore, it is better not to fall into these scale bands of destructive rays. Previously, researchers identified specific factors that could lead to the fact that particles in the belts will be strongly activated, but they could not infer the dominant cause.
Now new research from the THEMIS mission has helped to understand what is happening. The main culprit is local acceleration caused by EM waves, which are also called “choral” waves. They sound like birds chirping and accelerate particles. Establishing the root cause of improvements in the radiation belt provides key information for models predicting space weather that will protect our space technologies.
In the background magnetic field represented by the blue arrows, two electrons propagate to the right, performing an identical gyromotion. The circular polarized EM wave approaches the upper electron on the left There are two main reasons for particle excitation in the Van Allen belts: radial diffusion and local acceleration. Radial diffusion, often occurring during the solar storm, is a massive influx of particles, energy, and magnetic fields of the sun that can change our cosmic environment.
But scientists have seen that local acceleration caused by particles in contact with waves of fluctuating electric and magnetic fields can also provide energy for the particles. A new study showed that these interactions of wave particles are responsible for adding energy to particles around the Earth for 87% of the time.
The researchers understood that local acceleration works, because they observed mountains of energy particles growing in one place. This predicted a local acceleration mechanism, rather than sliding on the Earth in the form of diffusion.