Abstract:
Occurrence of electrostatic solitary waves (ESWs) is ubiquitous in space plasmas, e.g.,
solar wind, Lunar wake and the planetary magnetospheres. Several theoretical models have been
proposed to interpret the observed characteristics of the ESWs. These models can broadly be put into
two main categories, namely, Bernstein–Green–Kruskal (BGK) modes/phase space holes models,
and ion- and electron- acoustic solitons models. There has been a tendency in the space community
to favor the models based on BGK modes/phase space holes. Only recently, the potential of soliton
models to explain the characteristics of ESWs is being realized. The idea of this review is to present
current understanding of the ion- and electron-acoustic solitons and double layers models in multicomponent space plasmas. In these models, all the plasma species are considered fluids except the
energetic electron component, which is governed by either a kappa distribution or a Maxwellian
distribution. Further, these models consider the nonlinear electrostatic waves propagating parallel to
the ambient magnetic field. The relationship between the space observations of ESWs and theoretical
models is highlighted. Some specific applications of ion- and electron-acoustic solitons/double layers
will be discussed by comparing the theoretical predictions with the observations of ESWs in space
plasmas. It is shown that the ion- and electron-acoustic solitons/double layers models provide a
plausible interpretation for the ESWs observed in space plasmas.