The aurora borealis (and its southern twin, the aurora australis) is powered by the solar wind — a stream of charged particles blown outward from the Sun. Earth's magnetic field deflects most of this plasma around the planet, carving out a teardrop-shaped cavity called the magnetosphere. Where the interplanetary magnetic field points southward, it can partially cancel Earth's own field on the dayside, letting solar wind particles "reconnect" onto Earth's field lines and stream down them toward the poles, exciting atmospheric gases into a glow.
During the May 2024 Gannon superstorm — the strongest geomagnetic storm in over 20 years — the auroral oval expanded so far equatorward that aurora were reported as far south as Mexico and southern Europe, driven by a sustained, strongly southward IMF Bz.
A 3D Earth sits inside a magnetosphere shaped by the solar wind: charged particles stream in from the Sun, most are deflected around the compressed magnetopause, and a fraction funnel down dipole field lines into the polar atmosphere, lighting up simulated auroral curtains.
Southward IMF Bz opens a reconnection channel that lets more solar wind particles funnel along field lines into the cusp; brighter, wider auroral curtains and a higher simulated Kp index follow, mirroring real space-weather coupling.
Raise solar wind intensity and push Bz southward (negative) to compress the magnetopause and drive more particles down to the poles. Switch the emitting gas layer to see how altitude changes auroral colour, and rotate the view to see both poles.
Auroral green comes from molecular oxygen glowing near 100–150km, red from atomic oxygen above 200km, and rarer blue-violet fringes from ionised nitrogen below 100km — the same three-layer recipe reproduced by the curtain colours here.