  We have studied the evolution of ion-acoustic solitary waves (IASWs) in
pulsar wind. The pulsar wind is modeled by considering a weakly relativistic
unmagnetized collisionless plasma comprised of relativistic ions and
superthermal electrons and positrons. Through fluid simulations, we have
demonstrated that the localized ion density perturbations generated in the
polar wind plasma can evolve the relativistic IASW pulses. It is found that the
concentration of positrons, relativistic factor, superthermality of electrons,
and positrons have a significant influence on the dynamical evolution of IASW
pulses. Our results may provide insight to understand the evolution of IASW
pulses and their role in astrophysical plasmas, especially in the relativistic
pulsar winds with supernova outflow which is responsible for the production of
superthermal particles and relativistic ions.
