Turbulence In An Auto-Oscillating Complex Plasma

We present an experiment on the development of turbulence in a microparticle cloud in a low-temperature plasma laboratory onboard the International Space Station. First, the complex plasma cloud was stabilized with an alternating electric field. Once the stabilization was switched OFF, a so-called heartbeat instability developed in which the microparticles are oscillating radially. We show that the kinetic energy spectra develop a double cascade once the cloud becomes unstable. A double cascade has been predicted by Kraichnan and Leith for forced 2-D turbulence, but has only seldomly been observed in experiments. We also show that the reduced rates of energy and enstrophy transfer can be used to infer the excitation wavenumber k(exc), in good agreement with kexc obtained from the energy spectrum.