Government College (GC) University, Lahore, Pakistan
On Quasilinear Kinetic Model of Electromagnetic Electron Cyclotron and Electron Firehose Instabilities in Homogeneous and Inhomogeneous Solar Wind Plasmas
In solar wind plasma, characterized by temperature anisotropies of protons, alpha particles and electrons, different microinstabilities are known to be responsible for regulating the upper bounds of their respective temperatures. In our present work, a macroscopic quasilinear approach along with standard methodology of kinetic fluid modeling adopted to investigate the details of excitation, damping and saturation of electron temperature anisotropy-driven electromagnetic electron cyclotron (EMEC) and electron firehose (EFH) instabilities in homogeneous and in inhomogeneous (density and magnetic field profiles) solar wind plasmas. We constructed a closing set of self-consistent quasilinear equations constituting the particle kinetic, wave energy density and linearized Vlasov equations with the aid of single electrons component and halo component bi-Maxwellian model distributions. In our present technique, the solutions of kinetic equations inherently contain the so-called anisotropy-beta inverse relationship such that the empirical fitting is automatically reproduced at the end of each quasilinear calculation. Nevertheless, the empirical formula, which is built from consideration of linear analysis, cannot predict the timescale of instability saturation or the asymptotic wave energy density. Such an approach amounts to global-kinetic solar wind modeling suggested in the literature, and to reproduce the so-called "Bale" diagram.