Investigation of Lower Hybrid Drift Instability turbulence in the terrestrial magnetotail with fully kinetic, realistic mass ratio Multi-Level Multi-Domain simulations and comparison with observations

Abstract:

The kinetic, semi-implicit, adaptive Multi-Level Multi-Domain (MLMD) method is used to simulate, at realistic mass ratio, the development of turbulence generated by the Lower Hybrid Drift Instability (LHDI) in the terrestrial magnetotail over a large range of wavenumbers. The MLMD method reduces the cost of Particle in Cell (PIC) simulations by using higher temporal and spatial resolution only in a small part of the entire domain [Innocenti13, Beck14, Innocenti15]. This reduction in computational cost allows to increase the range of wavenumber simulated with respect to “traditional” PIC simulations and makes the MLMD method a useful approach to explore the multi scale nature of turbulent processes.

The power spectra of the fluctuations of the perpendicular electric field and of the magnetic field are studied at wavenumbers and times that allow to appreciate the onset of the electrostatic and electromagnetic LHDI branches and of the ion-ion kink instability. The coupling between electric and magnetic field fluctuations observed in Norgren [2012] for high wavenumber LHDI waves in the terrestrial magnetotail is verified. A break in the magnetic field fluctuation spectra at kdi ∼ 30, with di the ion skin depth and k the perpendicular wavenumber, is observed at early simulated times, Ωcit < 6, with Ωci the ion cyclotron frequency. It is explained with the initial decoupling of electric and magnetic field fluctuations at intermediate and low wavenumbers prior to the development of the electromagnetic LHDI branch. It is observed that the coupling is mediated by the electron current in the electrostatic and electromagnetic LHDI wavenumber range and by the ion current in the kink instability wavenumber range.

M. Innocenti, G. Lapenta, S. Markidis, A. Beck, and A. Vapirev, JCP 238, 115 – 140 (2013).

A. Beck, M. Innocenti, G. Lapenta, and S. Markidis, JCP 271, 430 – 443 (2014).

M. Innocenti, A. Beck, T. Ponweiser, S. Markidis, and G. Lapenta, CPC 189, 47 – 59 (2015).

Acknowledgements: we acknowledge NERSC, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy, Contract N. DE-AC02-05CH11231, PRACE SuperMUC machine, contract N. 2013091928, Fonds Wetenschappelijk Onderzoek, grant N. 12O5215N.