Coherent structures in space and astrophysical plasmas, and plasma propulsion devices
Rodrigo Andrés Miranda Cerda
UnB-Gama Campus and Plasma Physics Laboratory, University of Brasilia, (UnB), Brasilia-DF, Brazil
When: Aug 7, 2020 11:00 AM Sao Paulo
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Abstract:
Rare, large-amplitude coherent structures are responsible for non-Gaussian fluctuations, multifractality and synchronization among scales in intermittent turbulence. In this talk we will focus on the role of coherent structures in turbulent plasmas. We start discussing observational evidence from in-situ experiments in the interplanetary magnetic field turbulence. Then, we describe MHD simulations of a Keplerian shear flow in a regime of on-off intermittency. By computing the Shannon entropy in the spectral space we show that large-scale coherent structures are characterized by high degrees of Fourier amplitude-phase synchronization. We will also present particle-in-cell simulations of a two-dimensional model of a plasma propulsion device known as a Hall thruster. A prototype is currently being developed at the University of Brasilia. We demonstrate that the plasma in a Hall thruster displays turbulence and coherent structures arising from the ExB electron drift instability, which can affect the thruster efficiency.
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