Understanding Turbulence using Active and Passive Multipoint Measurements in Laboratory Magnetospheres

In a laboratory magnetosphere, plasma is confined by a strong dipole magnet, and interchange and entropy mode turbulence\footnote{Garnier, \textit{et al.}, \textit{Phys Plasmas}, \textbf{24}, 012506 (2017).} can be studied and controlled in near steady-state conditions.\footnote{Roberts, \textit{et al.}, \textit{Phys Plasmas}, \textbf{22}, 055702 (2015).} Turbulence is dominated by long wavelength modes exhibiting chaotic dynamics, intermitency, and an inverse spectral cascade. Here, we summarize recent results: (\textit{i}) high-resolution measurement of the frequency-wavenumber power spectrum using Capon's ``maximum likelihood method'',\footnote{Qian, \textit{et al.}, \textit{Undergraduate Poster Session; This meeting.}} and (\textit{ii}) direct measurement of the nonlinear coupling of interchange/entropy modes in a turbulent plasma through driven current injection at multiple locations and frequencies.\footnote{Abler, \textit{et al.}, \textit{Poster Category 1.8; This meeting.}} These observations well-characterize plasma turbulence over a broad band of wavelengths and frequencies. Finally, we also discuss the application of these techniques to space-based experiments and observations aimed to reveal the nature of heliospheric and magnetospheric plasma turbulence.