Nonlinear wave propagation of large amplitude ion-acoustic solitary waves in negative ion plasmas with superthermal electrons

Investigation of arbitrary amplitude nonlinear ion-acoustic solitary waves
which accompany collisionless positive–negative ion plasmas with high-energy electrons
(represented by kappa distribution) is presented. Arbitrary amplitude solitary
waves are investigated by deriving an energy-integral equation involving a Sagdeevlike
pseudopotential. The existence regions of solitary pulses are, defined precisely,
modified by the superthermality of energetic electrons. Furthermore, numerical
calculations reveal that both compressive and rarefactive pulses may exist for
negative ion mass groups in Titan’s atmosphere. The superthermality of energetic
electrons are found to modify the existence domains of large amplitude ion-acoustic
waves in Titan’s atmosphere. The dependence of solitary excitation characteristics on
the superthermal parameter, the negative ion concentration, the positive-to-negative
ions mass ratio, and the Mach number have been investigated. The present study
might be helpful to understand the excitation of fully nonlinear ion-acoustic solitary
pulses that may appear in the interplanetary medium and/or in the astrophysical
plasmas in general.