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Abstract:
We investigate kinetic turbulence in a reconnecting current sheet (RCS) with X- and O-nullpoints and to explore its link to the features of accelerated particles using particle-in-cell (PIC) approach. The model utilises a strong guiding field that leads to separation of the particles of opposite charges, generation of a strong polarisation electric field across the RCS and suppression of kink instability in the 'out-of-plane' direction. The accelerated particles of the same charge entering an RCS from the opposite edges are shown accelerated to different energies forming the `bump-in-tail' velocity distributions that, in turn, can generates plasma turbulence in different locations. The turbulence-generated waves produced by either electron or proton beams can be identified from the energy spectra of electromagnetic field fluctuations in the phase and frequency domains. From the phase space analysis we gather that the kinetic turbulence may be generated by accelerated particle beams, which are later found to evolve into a phase-space hole indicating the beam breakage. The collective turbulence power spectra are consistent with the upper hybrid waves, to occur in a vicinity of X-nullpoints, where the Langmuir are generated, while Bernstein waves generated on the edges of magnetic islands, The kinetic turbulence in parallel and perpendicular directions to the local magnetic field is also investigated with wavelet analysis showing noticeable lower hybrid turbulence occurring between the electron's gyro- and plasma frequencies. Fluctuation of the perpendicular electric field component of turbulence can be consistent with oblique whistler waves generated on the ambient density fluctuations by electron beams.
