Dark and grey electromagnetic electron-cyclotron envelope solitons in an electron-positron magnetoplasma

We present an investigation of the amplitude modulation of an external magnetic field-aligned right-hand circularly polarized electromagnetic electron-cyclotron move in a strongly magnetized electron-positron plasma. It is shown that the dynamics of the modulated EMEC wave packet is governed by a, cubic nonlinear Schrodinger equation. The latter reveals that a modulated wave packet can propagate W the form of either a dark or a grey envelope Won. This result could have relevance to he transport of electromagnetic move energy over long distances via envelope solitons in the magnetospheres of pulsars and magnetars