Solar and Experimental Plasma Physics Synergy
Nonlinear waves and shocks in non-Maxwellian Space plasmas: existence and propagation characteristics from first principles
Ioannis Kourakis
Manfred A. Hellberg
Queen's University Belfast
Space plasmas are often characterized by the presence of energetic particles in the background, due to various electron acceleration mechanisms [1]. 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
[2]. 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 [3].

We review, from first principles, of the effect of excess superthermality on the characteristics of electrostatic nonlinear plasma modes. We employ a kappa distribution function [1] to model the deviation of a plasma constituent (electrons, in general) from Maxwellian equlibrium. An excess in superthermal propulation modifies the charge screening mechanism, affecting the dispersion laws of both low- and higher frequency modes substantially. Various observations may thus be interpreted as manifestations of excess electron superthermality [2]. Focusing on the features of nonlinear excitations (shocks, solitary waves), we investigate the role of superthermality in their propagation dynamics (existence laws, stability profile) and dynamical profile [3]. The relation to other nonthermal plasma theories is briefly discussed.

[1] See V.M. Vasyliunas, J. Geophys. Res. 73, 2839 (1968), for a historical reference; also, V.Pierrard and M. Lazar, Solar Phys. 267, 153 (2010), for a more recent review.

[2] M. Hellberg et al, J. Plasma Physics 64, 433 (2000).

[3] S. Sultana, I. Kourakis, N.S. Saini, M.A. Hellberg, Phys. Plasmas 17, 032310 (2010); S. Sultana and I. Kourakis, Plasma Phys. Cont. Fus. 53, 045003 (2011);
S. Sultana, G. Sarri and I. Kourakis, Phys. Plasmas 19, 012310 (2012);
I. Kourakis, S. Sultana and M.A. Hellberg, Plasma Phys. Cont. Fusion, 54, 124001 (2012); G. Williams and I. Kourakis, Plasma Physics and Controlled Fusion 55, 055005/1-13 (2013).


09:00 - 10:30
EX - C33 (150)