Cylindrical Ion Acoustic Soliton in Plasma with Negative Ion

抄録

Cylindrical ion acoustic solitons are investigated theoretically and numerically in a plasma with negative ion. In a theoretical part, we derive a cylindrical Korteweg-de Vries equation for an ion acoustic wave. The sign of nonlinear coefficient depends on the negative ion density. At the critical density of the negative ion where the nonlinearity of the Korteweg-de Vries equation vanishes, the ion acoustic wave is described by a cylindrical modified Korteweg-de Vries equation, and in the vicinity of the critical density, it is described by a combined cylindrical equation of the Korteweg-de Vries and modified Korteweg-de Vries types. The change of a soliton amplitude due to the geometrical effect is analytically obtained in two limiting cases when the geometrical effect is much stronger or weaker than the nonlinear and dispersive effects. In the numerical calculation, the theoretical prediction for the change of the soliton amplitude is verified.