Abstract
Non-linear ion acoustic waves propagating in a plasma of warm electrons and one or more streams of cold ions are investigated. A hydrodynamical model which employs ion fluid streams interacting among themselves through the electron pressure gradient is used, isothermal electrons being assumed. Though the present model assumes charge neutrality, it enables us to show how large amplitude disturbances become steeper, tending to form shocks or inversely how discontinuous initial disturbances are smoothed out. For a single fluid, the behaviour is the same as those of isentropic gas with γ equal to unity. However for multicomponent cases there exist conspicuous properties such as multi-stream instabilities. This paper discusses all these effects for the case of two streams. Simple waves are obtained by means of the method of characteristics; for the wave propagating faster than all the ions the compression leads to shock formation whilst the expansion to the instability, for the waves lower than all the ions the expansion leads to the shock formation and at the same time to instability and for the wave propagating with intermediate speed the situation is more complicated.
