In the polytropic zone of the solar wind, we have used the generalized polytrope pressure laws to investigate the dissipation of hydromagnetic waves and pressure anisotropy driven fluid instabilities in magnetized viscous plasmas including finite Larmor radius (FLR) corrections and non-ideal magnetohydrodynamic (MHD) effects. The modified dispersion properties have been analyzed in the MHD and Chew–Goldberger–Low (CGL) limits for typical conditions of solar wind and corona. The theoretical results are found to be in good agreement with the observational data, which shows that the MHD and CGL waves are dissipated due to viscous and Ohmic diffusion. The FLR and Hall parameters show destabilizing and stabilizing influence, respectively for the strong magnetic fields in the solar corona, and reversed effects in the case of weak magnetic fields in the solar wind. In the solar corona, the CGL wave dissipation attains the required damping rate in the minimum time than the MHD waves. The damping time is mainly associated with the considered parameters and was found to be larger for the MHD wave dissipation than the CGL wave dissipation. The theoretical results successfully demonstrate the role of the considered parameters on the reverse and forward shock waves and instabilities as observed in the solar wind parameters versus heliolatitude graph using Ulysses observations for r = 5.41 au. The results are helpful to explore the possibilities of MHD waves and pressure anisotropy driven fluid instabilities in the polytropic zone of the solar wind that will be most probably observed by Parker Solar Probe (PSP) mission.
The effect of Braginskii's full viscosity tensor on an infinite nonconducting, gravitating anisotropic plasma in which the medium is trapped in a strong magnetic field is discussed in the context of Braginskii's magnetohydrodynamic model with Chew-Goldberger-Low(CGL) double adiabatic approximation and Finite Larmor Radius (FLR) correction. Through linearization of the perturbed equations, the general dispersion relation is derived for the separate compression, shear and drift viscosity components as well as the FLR corrections. We investigate the stability for parallel and transverse perturbations with respect to the direction of the magnetic field, and both gravitational and fire-hose instabilities are found. The role of each viscous term is to suppress instability, but each component works in different ways. The FLR acts in a way that is very similar to the drift viscosity. The instability threshold is found to be independent of viscosity for compression and shear viscosity, but the both the drift viscosity and FLR corrections can change the critical wavenumber for the instability. The compression viscosity is most effective at reducing the growthrate of the gravitational instability, whereas the shear viscosity works to suppress the fire-hose instability. The result of present study may be useful for the study of large scale compression, shear and drift plasma flow in and around clusters of galaxies, galactic disks and for the solar and stellar wind.
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