Physics of Plasmas 18: 072902/1-10 (2011)
doi: 10.1063/1.3606365

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

Ashkbiz Danehkar$^{1}$ ¹, Nareshpal Singh Saini$^{1}$ ², Manfred A. Hellberg$^{2}$ and Ioannis Kourakis$^{1}$
$^{1}$ Centre for Plasma Physics, Department of Physics & Astronomy, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
$^{2}$School of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa

Date: Received: February 2, 2011; Revised: June 10, 2011; Accepted: July 21, 2011

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 $\kappa$ ). A nonlinear pseudopotential technique is employed to investigate the occurrence of stationary-profile solitary waves, focusing on how their characteristics depend on the spectral index $\kappa$ , 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 $\kappa$ .

PACS number: 52.35.Sb, 52.35.Mw, 52.35.Fp, 72.30.+q

Keywords: hot carriers, plasma electrostatic waves, plasma nonlinear processes, plasma solitons

Footnotes

...¹

Present address: Department of Physics & Astronomy, Macquarie University, Sydney, NSW 2109, Australia

...²

Present address: Department of Physics, Guru Nanak Dev University, Amritsar-143005, India