A Hybrid Kinetic Model of Asymmetric Thin Current Sheets with Sheared Flows in a Collisionless Plasma

Abstract

Abstract : A new model of equilibrium current sheets in a collisionless plasma incorporating ion flows that are asymmetric and sheared across the current sheet is developed. Ions are treated as single particles and electrons as a massless fluid. The resulting current sheet is a Vlasov equilibrium satisfying Ampere's law. The current sheet thickness is shown to be of the order of the ion Larmor radius. It is found that the structure of the current sheet depends on the distribution function of the ions entering the current sheet. A characteristic feature of this class of equilibria is that the pressure tensor is anisotropic and nondiagnonal while the reversing component of the magnetic field is similar to the hyperbolic tangent Harris field. The results show that the asymmetric sheared ion momentum flows as well as the off-diagonal pressure tensor elements plan an essential role in the force balance. The model is applied to current sheets co-moving with the solar wind and is directly compared with high-resolution WIND MFI magnetic field data and WIND 3DP particle data. The agreement is good. The theoretical results are scalable to collisionless plasmas in different regimes.