Nonplanar solitons collision in ultracold neutral plasmas

Collisions between two nonplanar ion-acoustic solitons in strongly coupled ultracold neutral plasmas composed of ion fluid and non-Maxwellian (nonthermal or superthermal) electron distributions are investigated. The extended Poincare-Lighthill-Kuo method is used to obtain coupled nonplanar Kortweg-de Vries equations for describing the system. The nonplanar phase shifts after the interaction of the two solitons are calculated. It is found that the properties of the nonplanar colliding solitons and its corresponding phase shifts are different from those in the planar case. The polarity of the colliding solitons strongly depends on the type of the non-Maxwellian electron distributions. A critical nonthermality parameter β_c is identified. For values of β ≤ β_c solitons with double polarity exist, while this behavior cannot occur for superthermal plasmas. The phase shift for nonthermal plasmas increases below β_c for a positive soliton, but it decreases for β > β_c for a negative soliton. For superthermal plasmas, the phase shift enhances rapidly for low values of spectral index κ and higher values of ions effective temperature ratio σ_*. For 2 ≲ κ < 10, the phase shift decreases but does not change for κ > 10. The nonlinear structure, as reported here, is useful for controlling the solitons created in forthcoming ultracold neutral plasma experiments.