Electron-acoustic solitary waves in the presence of a suprathermal electron component

Abstract

The nonlinear dynamics of electron-acoustic localized structures in a collisionless and unmagnetized plasma consisting of "cool" inertial electrons, "hot" electrons having a kappa distribution, and stationary ions is studied. The inertialess hot electron distribution thus has a long-tailed suprathermal (non-Maxwellian) form. A dispersion relation is derived for linear electron-acoustic waves. They show a strong dependence of the charge screening mechanism on excess suprathermality (through κ). A nonlinear pseudopotential technique is employed to investigate the occurrence of stationaryprofile solitary waves, focusing on how their characteristics depend on the spectral index κ, and the hot-to-cool electron temperature and density ratios. Only negative polarity solitary waves are found to exist, in a parameter region which becomes narrower as deviation from the Maxwellian (suprathermality) increases, while the soliton amplitude at fixed soliton speed increases. However, for a constant value of the true Mach number, the amplitude decreases for decreasing κ.

Electron-acoustic solitons in an electron-beam plasma system with kappa-distributed electrons

“…An increase in the number density of suprathermal hot electrons or the suprathermality (decreasing κ) also decreases the phase speed, in agreement with what found in Ref. [10]. …”

“…(34) and (36) given in Ref. [10] in the coldelectron limit (T e = 0). Figure 2 depicts the existence domain of electron-acoustic solitary waves in two opposite cases: a very low, and a very high value of κ.…”

Experimental observation of electron-acoustic wave propagation in laboratory plasma

“…Similar role is played by the Alfven and whistler waves for propagation of magnetic disturbances parallel or near parallel to steady magnetic field, for example in magnetosphere plasma. Furthermore, EAW in nonlinear regime form solitary structures 11 and also provides a decay channel for the long wavelength Langmuir waves through nonlinear wave interactions 12 . In space plasma, analysis of the broadband electrostatic noise (BEN) in the terrestrial cusp of the magnetosphere and the hiss (high frequency field fluctuations) in the polar cusp region were found to corroborate to the generation of EAW [13][14][15][16] .…”

Obliquely propagating electron acoustic solitons in magnetized plasmas with nonextensive electrons

“…On the other hand, space plasma observations indicate clearly the presence of electron populations which are far away from their thermodynamic equilibrium (Vasyliunas, 1968;Leubner, 1982;Armstrong et al, 1983;Gill et al, 2006;Anowar and Mamun, 2008;Pakzad and Tribeche, 2010;Danehkar et al, 2011). Over the last two decades, a great deal of attention has been paid to nonextensive statistical mechanics based on the deviations of Boltzmann-GibbsShannon (B-G-S) entropy measure.…”