Magnetotail
Definition
The long tail of Earth's magnetic field stretching away from the Sun, where storm energy is stored before release.
In plain language
The solar wind blows Earth's magnetic field into a wind-sock shape millions of miles long. Energy piles up in this tail like a stretched rubber band โ and when it snaps back, the aurora erupts.
The science
The magnetotail comprises stretched lobes and a central plasma sheet extending hundreds of Earth radii anti-sunward. Flux loading during southward IMF thins the plasma sheet until near-Earth reconnection releases stored energy as substorms.
Why it matters for aurora viewing
The tail is the aurora's battery. Its charge/discharge rhythm is why displays surge in waves instead of glowing steadily.
See this in action on tonight's data.