Spatiotemporal dynamics of high-wavenumber turbulence in a basic laboratory plasma

Abstract

High-spatial resolution observation of high-wavenumber broadband turbulence is achieved by controlling the magnetic field to be relatively low and measuring with a azimuthally arranged multi-channel Langmuir array in a basic laboratory plasma. The observed turbulence consists of narrowband low-frequency fluctuations and broadband high-frequency turbulent fluctuations. The low-frequency fluctuations have a frequency of about 0.7 times the ion cyclotron frequency and a spatial scale of 1/10 of the ion inertial scale. In comparison, high-frequency fluctuations have a higher frequency than the ion cyclotron frequency and spatial scales of 1/10–1/40 of the ion inertial scale. Two-dimensional correlation analysis evaluates the spatial and temporal correlation lengths and reveals that the high-wavenumber broadband fluctuations have turbulent characteristics. The measurements give us further understanding of small scale turbulence in space and fusion plasmas.