Studies of positrons are of interest to plasma research recently because they annihilate electrons, and because they have the same mass and opposite charge, they can be combined to form a neutral plasmas with a dynamical symmetry between the charge species. Both electron-ion (e-i) and electron-positron (e-p) plasmas form two-component plasma systems. The difference between the systems is that, in case of e-i plasma, the specific charge for an electron is much greater than that for an ion, while this quantity is the same for both components of the e-p plasma. And due this difference, the linear and nonlinear behaviour of waves in the e-p plasma change differently from those in the conventional e-i plasma.

By introducing positrons into e-i plasma and ions into the e-p plasma, one obtains a three component plasma system called electron-positron-ion (e-p-i) plasma. The (e-p) plasma are assumed to have existed in the early universe. Moreover, the e-p system appears in active galactic nuclei, pulsar magnetospheres and solar atmosphere. Since the most of the astrophysical plasmas contain ions besides the electrons and positrons, it is significant to study the wave motions in the e-p-i plasma. The three component electron-positron-ion (e-p-i) plasmas occur naturally in the astrophysical backgrounds and have been encountered in the laboratory experiments where positrons are used as probes to study transport in the tokamaks. Further e-p-i plasma can also result from pair production in a plasma due to the propagation of intense laser pulses.

At CPP we address various problems, such as solitary Alfven waves, double layers associated with kinetic Alfven waves, plasma maser interaction, in e-p and e-p-i plasmas.