Ion scale current sheet instabilities in kinetic plasma turbulence

Project: Ion scale current sheet instabilities in kinetic plasma turbulence

Numerical code: AIKEF
Duration of the project:  05.2018 - 
Principal investigator: Neeraj Jain
External collaborators:

• U. Mostchmann and H. Comisel (TU Braunschweig, Germany)
• Z. Vörös and Y. Narita (Austrian Academy of Sciences, Space Research Institute, Graz, Austria)

Summary:

A key unsolved problem of the physics of collisionless plasmas, e.g., solar wind and solar corona, is the irreversible dissipation of macroscopic energy without collisional viscosity and electrical resistivity. It is enabled by turbulent transfer of energy from macroscopic to kinetic scales where the energy is finally dissipated. In-situ multi-spacecraft (Cluster, MMS) space observations and numerical simulations of collisionless plasma turbulence show evidences of intermittent dissipation localized in and around kinetic scale current sheets self-consistently formed in the turbulence. Plasma instabilities in these current sheets can provide the collisionless dissipation and determine the associated properties of kinetic plasma turbulence, e.g., the ion-scale break in magnetic field spectra and non-monotonous scale dependence of wave-vector anisotropy. Role of kinetic scale current sheet instabilities in determining the dissipation and the turbulence properties is, however, not clear yet.

Goal of this project is to investigate the role of ion-scale plasma instabilities, which are likely to grow in current sheets formed in ion kinetic plasma turbulence, in determining the ion-scale properties of the turbulence, in particular, location of the ion-scale break and non-monotonous scale dependence of wave-vector anisotropy. The goal is achieved by:

1. carrying out 3-D hybrid simulations (ions as particles and electrons as inertia-less fluid) of ion-kinetic plasma turbulence using the A.I.K.E.F. code of the TU Braunschweig,
2. identifying and characterizing the current sheets formed in the turbulence,
3. studying nonlinear evolution of plasma instabilities in individual laminar current sheets with free energy sources and parameters typical of the current sheets of the turbulence and
4. comparing the properties of the turbulence with the corresponding properties of the nonlinear state of the evolution of individual current sheets.

We also compare our results for various values of ion plasma beta in the range 0.1-10 with MMS/CLUSTER observations of current sheets and turbulence in collaboration with the space research group at Austrian Academy of Science, Space Research  Institute, Graz, Austria.