Cosmic-Ray Air Shower

Cosmic-ray air shower

A cosmic ray hits the top of the atmosphere and sets off a cascade of millions of particles. This page runs a small Monte Carlo simulation in your browser, in the spirit of the CORSIKA pictures: red electrons, positrons and photons, green muons, blue hadrons. Every press of New shower gives a different random shower.

Primary particle

Energy:

Zenith angle:

Ground level

Auto-rotate Speed Sound e± / γ Muons Hadrons Width ×

First interaction

Shower maximum X_max

Particles at max

e± at ground

Muons at ground

Tracks simulated

Press ⛶ (or F) for full screen. Drag to look around in 3-D, even while the shower is still growing: sideways turns it, up and down tilts it so you can see the footprint on the ground. The width is stretched so you can see it: real showers are only a few hundred metres wide but ~10 km long.

Longitudinal profile

Footprint on the ground

A teaching model, not CORSIKA itself: it uses an exponential atmosphere, the Heitler picture for e±/γ cascades (each e± or γ splits about every ln 2 radiation lengths, X₀ = 36.7 g/cm²), a simple pion-production model for hadrons, π⁰ → γγ, charged pions decaying to muons, multiple scattering, and Hillas “thinning” (weighted sampling of low-energy particles) to stay fast. The real CORSIKA from KIT tracks every particle with full interaction models.