Earth’s Magnetosphere

The magnetosphere is a complex and dynamic structure shaped by the solar wind, a continuous stream of charged particles (mostly protons and electrons) flowing from the Sun. On the side facing the Sun, the magnetosphere is compressed and extends about 10 Earth radii. The outer boundary is the magnetopause. Upstream of the magnetopause is the bow shock, where the supersonic solar wind abruptly slows down. On the opposite side, the night side, the magnetosphere is stretched out into a long tail, the magnetotail, which extends hundreds of Earth radii.

Within the magnetosphere are the Van Allen radiation belts, two doughnut-shaped zones of energetic charged particles trapped by the magnetic field. The inner belt consists mainly of high-energy protons, while the outer belt is primarily composed of high-energy electrons. These belts pose a hazard to satellites. The magnetosphere also channels solar particles towards the magnetic poles, where they collide with atoms in the upper atmosphere, causing the spectacular auroras (aurora borealis and aurora australis). During intense solar événements, known as geomagnetic storms, the magnetosphere can be severely compressed, leading to auroras at lower latitudes and posing risks to power grids and communication systems.