Filamentation instability of a large amplitude whistler wave

A filamentation instability of a large amplitude whistler wave is observed in a laboratory experiment. The wave is launched in a large uniform magnetoplasma from antennas which produce a diverging energy flow in the linear regime. At large amplitudes (B w /B 0≃1%) the radiation pressure gives rise to a density depression originating from the antenna. The wave refracts into the density minimum which enhances the pressure and a filamentation instability develops. It saturates when a long field‐aligned density trough is formed in which the wave is almost perfectly ducted. The temporal and spatial evolution of the self‐ducting process are shown. The duct formed by the high power whistler wave also guides small amplitude whistlers over a wide range of frequencies.