A magnetosphere is a vast, invisible shield surrounding a planet, created when the planet's magnetic field carves out a protective bubble in space against the relentless stream of charged particles from the Sun, known as solar wind. This dynamic boundary typically extends tens of thousands of kilometers into space, far beyond a planet's atmosphere.</p><p>Earth's magnetosphere stretches approximately 65,000 kilometers toward the Sun and forms a long tail extending over 6 million kilometers on the night side. When solar wind particles traveling at 400-800 kilometers per second encounter this magnetic barrier, most are deflected around our planet. However, some particles become trapped, creating the Van Allen radiation belts—donut-shaped regions of energetic particles discovered in 1958 by Explorer 1.</p><p>The magnetosphere's protective role is dramatically visible during geomagnetic storms, when solar wind breaches weaker regions near the poles, creating spectacular auroras. Without this shield, solar radiation would gradually strip away our atmosphere, as likely happened to Mars, which lost most of its magnetic field billions of years ago.</p><p>Jupiter possesses the solar system's most powerful magnetosphere—20,000 times stronger than Earth's—extending beyond Saturn's orbit. This colossal magnetic bubble traps so much radiation that it would be lethal to unprotected astronauts, demonstrating how magnetospheres profoundly influence planetary habitability and space exploration.