Sub and super-luminar propagation of structures satisfying Poynting like theorem for incompressible GHD fluid model depicting strongly coupled dusty plasma medium

TL;DR

This paper investigates the propagation of dipole structures in an incompressible generalized hydrodynamic (GHD) model of strongly coupled dusty plasma, revealing sub and super-luminar behaviors and deriving a Poynting-like conservation law.

Contribution

It introduces a detailed analysis of transverse shear wave emission by structures in the GHD model and formulates a new conservation law analogous to Poynting's theorem for these systems.

Findings

Dipole structures emit shear waves in sub and super-luminar regimes.

In sub-luminar regime, structures are engulfed by emitted shear waves, losing identity.

In super-luminar regime, structures propagate with minimal distortion, resembling wake emission.

Abstract

The strongly coupled dusty plasma has often been modelled by the Generalized Hydrodynamic (GHD) model used for representing visco-elastic fluid systems. The incompressible limit of the model which supports transverse shear wave mode is studied in detail. In particular dipole structures are observed to emit transverse shear waves in both the limits of sub and super - luminar propagation, where the structures move slower and faster than the phase velocity of the shear waves, respectively. In the sub - luminar limit the dipole gets engulfed within the shear waves emitted by itself, which then backreacts on it and ultimately the identity of the structure is lost. However, in the super - luminar limit the emission appears like a wake from the tail region of the dipole. The dipole, however, keeps propagating forward with little damping but minimal distortion in its form. A Poynting like conservation law with radiative, convective and dissipative terms being responsible for the evolution of W , which is similar to `enstrophy' like quantity in normal hydrodynamic fluid systems, has also been constructed for the incompressible GHD equations. The conservation law is shown to be satisfied in all the cases of evolution and collision amidst the nonlinear structures to a great accuracy. It is shown that monopole structures which do not move at all but merely radiate shear waves, the radiative term and dissipative losses solely contribute to the evolution of W. The, dipolar structures, on the other hand, propagate in the medium and hence convection also plays an important role in the evolution of W.