Evolution of electromagnetic soliton during laser-plasma interaction in an electron-positron-ion plasma having constant density gradient

Laser propagation in an electron-positron-ion (EPI) plasma medium having a constant density gradient is studied for the soliton evolution in the presence of a parallelly applied strong magnetic field. In a nonlinear regime, laser-plasma interaction forms an electron density hill that moves backward due to the density gradient. This hill localizes laser energy by the mechanism of resonance absorption (ωl =ωpe) and remains stable for a longer period, qualifying for the evolution of electromagnetic soliton. The position of the soliton from where it starts moving backward depends on the slope of the linear density variation. If the slope increases, then the position of the soliton is closer to the plasma boundary (x = 0). Another interesting property of the soliton is that its height decreases, and width increases as the temperature of plasma species rises. We simulate this phenomenon of electromagnetic soliton evolution in 1-D and 2-D by using Particle-In-Cell (PIC) simulation using the EPOCH-4.17.10.