What causes Earth’s bow shock?
Earth’s magnetic field acts as an obstacle to the solar wind, meaning this plasma streaming from the Sun needs to be deflected around our planet. But because the solar wind is supersonic, the only way this can occur is through a shock wave known as the bow shock.
A shock wave is an extreme sound wave where the pressure (density and temperature) has built up, forming a sharp jump in values over a short amount of distance. Earth’s bow shock borrows its name from an analogous effect for boats: when a boat travels through water its bow (front) pushes the water out of the way, but if the boat is travelling faster than the speed of the water waves the water will pile up, forming a shock.
The sonic boom around jet fighters is another example of the same effect. While most people think of shock waves as a bad thing due to their destructive role in explosions, Earth’s bow shock – as well as those for boats and aircraft – actually protects us. By slowing down and deflecting many of the charged particles from the Sun away from us, the bow shock helps prevent this ionising
radiation from bombarding our planet