Electrostatic excitations in non-Maxwellian space plasmas

Highlighting some basic properties of plasmas and relevant applications, we present preliminary stuff on linear and nonlinear waves. Space and astrophysical plasmas may be composed of superthermal (accelerated) particles, which can be appropriately described by the non-Maxwellian (Kappa) distribution function rather than traditional Maxwellian distribution. It is now well-known that wave propagation characteristics are significantly altered with the non-Maxwellian distribution functions. In this model, nonlinear properties of arbitrary amplitude ion-acoustic waves (IAWs) are investigated in an electron-positron-ion magnetoplasma, in which singly ionized cold ions are taken as inertial, whereas superthermal electrons and positrons are described by the Kappa distribution. Reducing the hydrodynamic equations to a pseudo-energy-balance equation, the existence conditions for IAWs are discussed. It is shown that only subsonic nonlinear IAWs can propagate in a non-Maxwellian magnetoplasma, affected significantly by the variation of plasma parameters. The relevance of nonlinear excitations in interstellar medium is pointed out, where superthermal electrons and positrons are present.