Magnetosphere
The bubble of space controlled by Earth's magnetic field. It deflects the solar wind, and solar storms can squeeze it hard.
Earth behaves like a giant bar magnet, and its magnetic field reaches far out into space. The region it controls is the magnetosphere. The Sun constantly blows a stream of charged particles, the solar wind, against it. The wind squashes the side facing the Sun and stretches the night side into a long tail.
The outer boundary is called the magnetopause. On the sunward side it normally sits about 6 to 10 Earth radii away, that is, roughly 40,000 to 64,000 km. Most of the solar wind is slowed at a shock wave in front of it and flows around the planet instead of hitting the atmosphere.
When a fast coronal mass ejection arrives, the magnetopause is pushed inwards and the field at the ground can change within minutes. In August 1972 it was squeezed to about 5.2 Earth radii. Those rapid changes drive currents in power lines and can fool instruments that sense magnetism.
A common misconception is that the magnetosphere is a hard, fixed shell. In fact it is constantly breathing, growing and shrinking as the solar wind changes, and some solar particles leak in near the poles, where they light up the aurora.
