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磁场如何保护行星免受太阳风的损害？

Planets with global magnetic fields, like Earth, deflect charged particles from the solar wind outward.
This deflection creates a protective bubble called the magnetosphere that surrounds the planet.
Without it, solar wind would gradually strip away atmospheres — as likely happened on Mars.
Earth’s field originates from swirling molten iron in its outer core, generating electric currents.
The magnetosphere channels some particles toward the poles, where they create auroras upon hitting air molecules.
Venus and Mars lack strong internal dynamos, so their atmospheres erode more easily over time.
Satellites like ESA’s Swarm mission map magnetic field changes to monitor planetary shielding strength.
Even weak fields can reduce atmospheric loss significantly if combined with thick atmospheres or ionospheres.
During solar storms, the magnetosphere compresses but usually holds — though power grids may still be affected.
Understanding this shield helps scientists assess habitability of exoplanets orbiting active stars.