Each vertical ray approximates a bundle of charged particles spiralling down a single geomagnetic field line. Instead of drawing a straight beam, every ray's x-position is bent by a travelling horizontal wave x(y,t) = x0 + fold(y,t) so neighbouring rays fold together into the curtain's characteristic pleats, the same way a real aurora ripples as the underlying field lines and particle sheet flex.
Each ray is colour-banded by altitude, following the real collision chemistry of the upper atmosphere:
- ~100–150 km — excited atomic oxygen relaxes with its green 557.7 nm line, the aurora's most common colour.
- above ~150–300 km — oxygen is sparser and slower to de-excite, favouring its red 630.0 nm forbidden line at the curtain's rippling top.
- below ~100 km — the fastest, most energetic particles penetrate deepest and excite ionised nitrogen's blue/violet bands, visible as a faint fringe along the curtain's lower edge.
The solar wind intensity slider drives three things at once, mirroring real space weather: particle flux (ray brightness and count active), penetration depth (how far down the curtain's base reaches, i.e. how low the green/blue boundary sits), and curtain height (how far the red cap extends upward) — a stronger solar wind pushes more, faster particles deeper into the atmosphere and brightens/extends the whole display, just as a geomagnetic storm does.
Approximation: a 2D vertical cross-section (not a full 3D volume), a simplified two-boundary altitude→colour mapping rather than a continuous emission spectrum, and a procedural horizontal fold wave standing in for real magnetospheric current-sheet dynamics.