Solar wind is a constant stream of charged particles flowing from the Sun. It carries its own magnetic field, the IMF (Interplanetary Magnetic Field).

As this fast-moving solar wind approaches Earth, it encounters the bow shock — a standing shockwave where the flow suddenly slows, heats up, and becomes more turbulent, before reaching the magnetosphere, Earth's magnetic field, which acts as a shield against solar wind.

When the IMF points north, it aligns with the Earth's field and the solar wind mostly flows around the magnetosphere: the "gate" stays closed.

But when the IMF points south, the fields oppose each other. This allows them to connect and reconnect at the magnetopause (the sun-facing boundary of the magnetosphere), opening a gate that lets solar wind energy pour in.

That energy is carried around to the night side of the Earth (the magnetotail), where it builds up until a substorm — a sudden snap of magnetic reconnection — releases it along field lines towards the high-latitude upper atmosphere, creating the aurora.

This animation shows that process in real time: solar wind flowing in from the left, slowing at the bow shock, deflecting around the magnetosphere, and, when conditions are right, being guided down into the upper atmosphere to produce aurora.

By default the animation reflects live space weather conditions. You can switch to simulated conditions which map to geomagnetic storm levels (G1-G5).

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