Cusp and Regular Ion-Acoustic Solitons

Cups and regular smooth solitons are studied using the fluid model in cylindrical geometry for parallel propagating ion-acoustic waves in a low β plasma. It is found that smooth solitons only occur in the supersonic regime, whereas cusp solitons occur both in supersonic and subsonic regimes. In the supersonic regime, the amplitude and the width of cusp solitons increase when the Mach number M increases and initial electric field E ₀ decreases. However, the amplitude of smooth regular solitons increases and their width decreases when E ₀ increases and M decreases. For the subsonic case, both the amplitude as well as the width of a cusp solitons increase when M increases and E ₀ decreases. Corresponding to these cusp and regular solitons, bipolar electric field structures are also studied. These results may be helpful in understanding the properties of ion-acoustic regular and cusp solitons in space plasmas.