Modelling of Electrostatic Solitary Waves and Shocks in Non-Maxwellian Plasmas: A Review of Recent Results
Abstract:Space plasmas are often characterized by the presence of energetic particles in the background, e.g. due to various electron acceleration mechanisms . This phenomenon is associated with a power-law dependence at high (superthermal) velocity values, modeled by a kappa-type distribution function, which reproduces observed data more efficiently that the standard Maxwellian distribution approach . It has been shown from first principles that this ubiquitous superthermal feature of plasmas may alter the propagation characteristics of plasma modes, and modify the plasma screening properties .
In this presentation I will review, from first principles, the effects of a non-Maxwellian electron distribution on the characteristics of electrostatic plasma modes. A kappa distribution function  is employed to model the deviation of a plasma constituent (electrons, in general) from Maxwellian equlibrium. It will be shown that the excess in superthermal propulation modifies the charge screening mechanism, affecting the dispersion laws of both low- and higher frequency modes significantly. Various experimental observations may thus be interpreted as manifestations of excess superthermality . Focusing on the features of nonlinear excitations (shocks, solitons), we investigate the role of superthermality in their propagation dynamics (existence laws, stability profile) and dynamical profile . The relation to other nonthermal plasma theories is briefly discussed.
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