Arbitrary amplitude ion-acoustic solitary excitations in the presence of excess superthermal electrons
- Centre for Plasma Physics, Department of Physics and Astronomy, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)
- School of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000 (South Africa)
Velocity distribution functions with an excess of superthermal particles are commonly observed in space plasmas, and are effectively modeled by a kappa distribution. They are also found in some laboratory experiments. In this paper we obtain existence conditions for and some characteristics of ion-acoustic solitary waves in a plasma composed of cold ions and {kappa}-distributed electrons, where {kappa}>3/2 represents the spectral index. As is the case for the usual Maxwell-Boltzmann electrons, only positive potential solitons are found, and, as expected, in the limit of large {kappa} one recovers the usual range of possible soliton Mach numbers, viz., 1<M<1.58. For lower values of {kappa}, modeling the presence of a greater superthermal component, the range of accessible Mach numbers is reduced. It is found that the amplitude of the largest possible solitons that may be generated in a given plasma (corresponding to the highest allowed Mach number for the given plasma composition) falls off with decreasing {kappa}, i.e., an increasing superthermal component. On the other hand, at fixed Mach number, both soliton amplitude and profile steepness increase as {kappa} is decreased. These changes are seen to be important particularly for {kappa}<4, i.e., when the electrons have a 'hard' spectrum.
- OSTI ID:
- 21277243
- Journal Information:
- Physics of Plasmas, Vol. 16, Issue 6; Other Information: DOI: 10.1063/1.3143036; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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