On Electromagnetic Field Structure Near the Magnetized Body and Action on it by Reshaping of the Particle Distribution Function of the Incoming Supersonic Collisionless Plasma Flow

Abstract

We consider interaction of a magnetized body with a supersonic (M>1) flow of rarefied hot high plasma beta weakly magnetized collisionless plasma characterized by particle velocity distribution functions (VDF) of different shapes. A body has internal degrees of freedom defined by magnetic dipole/toroidal moments and, by virtue of the driving Ampere force in the plasma, can nonlinearly interact with acoustic modes of the flow, which result in an e. m. induced acoustic nontransparent “cloak”, where M>>1. Here we study the electromagnetic driving wake field around a body and obtain the governing dimensionless parameters of e.m. interaction. In a rarified hot plasma (artificial or natural) near the body we study the problem using Vlasov/Maxwell kinetic approach where the flow is not a fluid, but a set of charged particles. Via the Vlasov equation, the incoming plasma flow is characterized by a dielectric permittivity tensor. For isotropic VDF considered here, the tensor is of diagonal form. Via components of the tensor, we can express dielectric, magnetic, and conductive (resistive) properties of the incoming flow of particles and perturbations of the flow. These properties are expressed via the shape of the VDF and via the HD parameters. For the direct motion process in the supersonic and subthermal to electron regime, the components of the tensor have a specific particular form and are expressed via dimensionless parameters (numbers). It is the acoustic Mach number that characterizes the longitudinal component of the tensor. Dimensionless electromagnetic parameters of the momentum and of the energy anisotropy of the flow characterize transverse components of the diagonal tensor, i.e., electromagnetic properties of the flow. The last parameters are expressed differently via shape characteristics of the VDF. Momentum anisotropy of the VDF defines e.m friction, and energy anisotropy of the VDF defines e.m. dynamic pressure on the magnetized body. The ratio of the e.m. anisotropy parameters defines the governing e.m. parameter G, which is independent of governing acoustic parameter M. The number G characterizes the ratio of diamagnetic to resistive currents in a plasma; the resistive currents are formed by resonant particles. For G 1 we have diamagnetic properties with the formation of a “magnetosphere” defined by inductive e.m. fields. The negative number G= 1 appears in the Quasi Current Free plasma dynamic regime of e.m. unstable plasma. As the parameter G changes adiabatically from small to large values we have a transition from the resistive state with magnetotail (wake) configuration to a new topological diamagnetic compact dipolized state. We calculated a fine 3D structure of the wake for G<<1. The 3D structure is defined via new plasma dispersion scales defined via the shape of the VDF and plasma density. Nonadiabatic change in the VDF shape provides a change in GV and the formation of e.m. plasmoids in the wake of the body. We calculated G=GV for flows with different VDFs shapes, in particular, for the “kappa” power-law VDF with different signs of the parameter “kappa”.