Observations made with #nasa´s THEMIS (Time History of Events and Macroscale Interactions during Substorms). revealed highly accelerated particles in a region beyond the bow shock. In the upper parts of the atmosphere, the #Earth´s magnetic field is constantly deflecting the solar wind, which consists of a stream of supersonic charged particles from the sun. These particles are deflected away from earth in a region known as the bow shock, while others are reflected back in a region called the foreshock, causing a turbulence of particles there. New observations with NASA´s THEMIS have revealed that this turbulent region is able to accelerate electrons to speeds that approach the speed of light, making them extremely energetic.

Particles accelerated in regions beyond earth's magnetic field

Particles, including the solar wind and the interstellar medium, streaming towards the earth encounter a protective barrier known as the earth´s magnetic field that surrounds the planet. This field has a region known as the bow shock that faces the sun. When particles meet the bow shock, they are slowed down and deflected away from their path toward the earth, while others are reflected back in the direction of the sun. These particles form the foreshock, which is a region where ions and electrons are highly accelerated.

Magnetic activity in the foreshock

Originally, scientist had thought that the acceleration of electrons and ions in the foreshock was due to the bouncing back and forth of the particles between this region and the bow shock in a process known as the shock drift acceleration; however, new observations suggest that the particles can also get energized through electromagnetism in the foreshock, which until now is the best explanation for the phenomenon; however, further observations are needed to give a conclusive answer to this process.

THEMIS observations

The discovery of this process was done by one of the five THEMIS mission satellites that orbit the earth. The group of five THEMIS satellites intent to study the way in which the earth´s magnetosphere captures and interacts with the solar wind, so as to comprehend the mechanisms that causes auroras at the poles. The orbits of these satellites around the earth allowed them to fly close to the premises of the foreshock region, allowing the observation of highly #accelerated electrons, revealing that the high energies were not produced by interactions with the solar wind, but were produced by other sources within the foreshock region itself.

This discovery has opened new questions as the way in which electrons can be accelerated to high speeds in regions different from what was previously thought. The findings may open new perspectives as to how electrons are accelerated not only in shocks on earth but also in other shocks of bodies comprising the whole universe, leading to a better understanding at how to deal with the dangers to which astronauts are exposed when in space.