Self-Ducting of Large-Amplitude Whistler Waves

Whistler waves are launched from an electric dipole of length $L$ in a large-volume laboratory plasma. With increasing wave amplitude the radiation pattern narrows and finally forms a duct of diameter $d\simeq L\simeq {\lambda }_{\parallel }$. The ducted waves propagate nearly undamped. The observed nonlinear effects are explained by wave-particle interactions.