十万个为什么·科学阅读30篇（4）

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地球磁场如何抵御太阳风？

Earth’s molten iron core generates a powerful magnetic field extending far into space.
This invisible shield deflects most charged particles streaming from the Sun’s outer atmosphere.
Without it, solar wind would gradually strip away our atmosphere like Mars lost its.
Some particles do enter near the poles, where field lines converge and guide them downward.
There, they collide with atmospheric gases and create the shimmering auroras seen near Arctic and Antarctic circles.
NASA satellites monitor real-time changes in magnetosphere shape during solar storms.
During strong geomagnetic storms, induced currents can disrupt power grids and satellite operations.
Animals such as sea turtles and migratory birds rely on this field for navigation across continents.
The field strength fluctuates slowly over centuries and even reverses polarity every few hundred thousand years.
Scientists map these variations using ancient lava flows that locked in magnetic orientation when cooling.