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

Ashkbiz Danehkar,
Centre for Plasma Physics, Department of Physics & Astronomy, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
Present Address: Department of Physics & Astronomy, Macquarie University, Sydney, NSW 2109, Australia

Nareshpal Singh Saini,
Centre for Plasma Physics, Department of Physics & Astronomy, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
Present address: Department of Physics, Guru Nanak Dev University, Amritsar-143005, India

Manfred A. Hellberg,
School of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa

Ioannis Kourakis
Centre for Plasma Physics, Department of Physics & Astronomy, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom

Date: Received 2 February 2011; accepted 10 June 2011; published online 21 July 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 $\kappa$.
 
Keywords: hot carriers, plasma electrostatic waves, plasma nonlinear processes, plasma solitons.
 
PACS Nos.: 52.35.Sb, 52.35.Mw, 52.35.Fp, 72.30.+q
 
Journal Reference: A. Danehkar, N. S. Saini, M. A. Hellberg, and I. Kourakis. Physics of Plasmas, 18:072902/1–10, 2011. doi:10.1063/1.3606365