Nonlinear low-frequency structures in an electron-positron-ion plasma

Nonlinear ion cyclotron and ion-acoustic waves have been studied in an electron-positron-ion plasma. Using Boltzmann distributions for the electrons and positrons and fluid equations for the ions, a set of nonlinear equations in the rest frame of the propagating wave is derived and numerically solved for the electric field. A scan of parameter space reveals a range of solutions for the parallel electric field, from sinusoidal to sawtooth to highly spiky waveforms. The results are compared with satellite observations.