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We present a calculation of the natural oscillation spectrum of a bounded non-neutral ultra-cold plasma. The frequencies of these oscillations are recorded in experiments as absorption resonances of high-frequency electric field. Dependence of the frequency of these resonances on the charge imbalance and on the expansion time is obtained. Good agreement with experiment is noted

We present a general expression for the probability distribution function of electric field in a plasma cloud formed by the impact of a laser pulse on a gas or a solid body. We also present the results of numerical calculation of this function for the case of non-interacting particles depending on the plasma cloud size. It takes into account the ionic microfield and the macrofield arising from the charge imbalance. As the charge imbalance increases, the effect of a sharp increase in the distribution function for large field values is observed. Good agreement between the calculation of the shift of the spectral line and the experiment is obtained. The results obtained are of crucial importance for diagnosing plasma in various applications., 5 pages, 3 figures

We present the results of direct simulation of the expansionof a two-component ultracold plasmafor various numbers of particles, densities, and electron temperatures. A description of the expansionprocess common to all plasma parameters is given. After the escape of fast electrons from the plasmacloud, the excess positive charge is localized at the outer boundary, in a narrow layer. This layerhas a characteristic front shape with a sharp drop in the charge concentration. The charged layerretains the remaining electrons during the entire expansion process. As the plasma expands, thespeed of movement of the charged layer becomes constant and significantly exceeds the sonic speedof ions. In addition, the dependence of the radial velocity of ions on the radius acquires a self-similarcharacter long before the final stage of expansion. On the basis of the calculation results, equationsand self-similar solutions are obtained. General dependences on plasma parameters are determined,which are compared with experimental data., 7 pages, 9 figures. This paper heve been submitted to Phys. Rev. E