Jucker, M.

Pavlenko, V.P.

Infoscience - École polytechnique fédérale de Lausanne

Generation and Stability of Large Scale Magnetic Structures in Electron Drift TurbulenceM. Jucker1 and V. P. Pavlenko  2 1Ecole Polytechnique Federale de Lausanne (EPFL),Centre de Recherches en Physique des Plasmas, Association EURATOM-Confederation Suisse, 1015 Lausanne, Switzerland2Uppsala University and EURATOM-VR Fusion Association, SE-751 20 Uppsala, SwedenThe generation of large scale flows by underlying small scale turbulence is  a  well  known  phenomenon  in  different  areas  of  current  research. Here,  we  turn  our  attention  to  the  magnetic  electron  drift  mode turbulence. The corresponding turbulent magnetic fluctuations are drift-type  modes  excited  in  non-uniform,  initially  non-magnetized  plasma, characterized by a frequency range in-between the electron and the ion plasma frequencies. Within the magnetic electron drift mode turbulence, we address the question of generation of large scale magnetic fields by small  scale  turbulent  magnetic  fluctuations  via  turbulent  Reynolds stress, as  well  as  their  subsequent  mutual  interactions.  For  the mathematical  description we have to take into account that  the total wave energy is conserved and contains both the part stored in small as well as large scale structures. We thus deal with a coupled system of two different parts of the same wave spectrum which cannot be addressed in isolation.  This  necessitates  a  nonlinear  theory  capable  of  describing magnetic electron drift wave and large scale magnetic fields spectra as interacting parts of one and the same spectrum. Such a self-consistent nonlinear model has been developed via a wave kinetic equation for a suitable action-like invariant. Having the spectral model equations in our hand, we focus on the dynamics  of  interacting magnetic  drift  wave - large scale field turbulence. The stability of such large scale structures is investigated in the kinetic regime and an instability criterion similar to the  known  Nyquist  criterion  in  kinetic  wave  theory  is  found.  This criterion is  then applied to a narrow wave packet,  where we find an amplitude threshold due to finite width of the wave spectrum in k-space.

Generation and Stability of Large Scale Magnetic Structures in Electron Drift Turbulence

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Generation and Stability of Large Scale Magnetic Structures in Electron Drift Turbulence

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Infoscience - École polytechnique fédérale de Lausanne