What is the aurora?

Aurora is light emitted by atmospheric particles high above ground (~80-500km) in response to being struck by energetic charged particles from space spiraling down along magnetic field lines. This works just like old CRT (Cathode Ray Tube) TVs and monitors where an electron gun bombards a screen with electrons, the screen being coated with phosphors emitting light of specific colors when struck by electrons. In other words, the Earth’s atmosphere acts like a giant, 3-dimensional TV screen during an auroral display, and what it shows is a visualization of Earth’s magnetic field (because the incoming charged particles follow the field lines).

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Credit: NASA/Goddard Space Flight Center Conceptual Image Lab