Cavitating Langmuir turbulence in the terrestrial aurora.

Langmuir cavitons have been artificially produced in Earth's ionosphere, but evidence of naturally occurring cavitation has been elusive. By measuring and modeling the spectra of electrostatic plasma modes, we show that natural cavitating, or strong, Langmuir turbulence does occur in the ionosphere, via a process in which a beam of auroral electrons drives Langmuir waves, which in turn produce cascading Langmuir and ion-acoustic excitations and cavitating Langmuir turbulence. The data presented here are the first direct evidence of cavitating Langmuir turbulence occurring naturally in any space or astrophysical plasma.