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Abstract
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The collisionless expansion of plasma with cold ions and nonextensive distributed electrons into vacuum
is investigated using a self-similar hydrodynamic model in both planar and nonplanar geometries. The
speed, size and the energy spectrum of ions in expanding plasma is studied in terms of nonextensivity
and geometry parameters. It is found that superthermal electrons with nonextensive distribution accelerate ions to higher speeds and creating a high energy tail in ion-energy spectrum compared to that with
Maxwellian electrons. The later may be useful in describing the high energy ions created in irregular
space plasma expansion or strong intense laser-plasma accelerated expansion. A generalized
Fokker-Planck like diffusion equation is obtained for plasmas with q-nonextensive electrons applicable
to different geometry of expansion. From numerical investigation, it is observed that the rates of diffusive
expansion for nonplanar geometries are different from planar ones. The anomalous character of diffusive
plasma expansion is studied and concluded that three distinct regimes depending on the q-parameter
value exists in all geometries.
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