Arbitrary amplitude ion acoustic solitons, double layers and supersolitons in a collisionless magnetized plasma consisting of non-thermal and isothermal electrons
Sandip Dalui, Sankirtan Sardar, Anup Bandyopadhyay
Abstract
Abstract Using Sagdeev pseudo-potential technique, we have studied the arbitrary amplitude ion acoustic solitons, double layers and supersolitons in a collisionless plasma consisting of adiabatic warm ions, non-thermal hot electrons and isothermal cold electrons immersed in an external uniform static magnetic field. We have used the phase portraits of the dynamical system describing the non-linear behaviour of ion acoustic waves to confirm the existence of different solitary structures. We have found that the system supports (a) positive potential solitons, (b) negative potential solitons, (c) coexistence of both positive and negative potential solitons, (d) negative potential double layers, (e) negative potential supersolitons and (f) positive potential supersolitons. Again, we have seen that the amplitude of the positive potential solitons decreases or increases with increasing n ch according to whether <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:mn>0</m:mn> <m:mo><</m:mo> <m:msub> <m:mi>n</m:mi> <m:mrow> <m:mi>c</m:mi> <m:mi>h</m:mi> </m:mrow> </m:msub> <m:mo><</m:mo> <m:msubsup> <m:mi>n</m:mi> <m:mrow> <m:mi>c</m:mi> <m:mi>h</m:mi> </m:mrow> <m:mrow> <m:mo>(</m:mo> <m:mi>c</m:mi> <m:mo>)</m:mo> </m:mrow> </m:msubsup> </m:mrow> </m:math> $0{< }{n}_{ch}{< }{n}_{ch}^{\left(c\right)}$ or <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:msubsup> <m:mi>n</m:mi> <m:mrow> <m:mi>c</m:mi> <m:mi>h</m:mi> </m:mrow> <m:mrow> <m:mo>(</m:mo> <m:mi>c</m:mi> <m:mo>)</m:mo> </m:mrow> </m:msubsup> <m:mo><</m:mo> <m:msub> <m:mi>n</m:mi> <m:mrow> <m:mi>c</m:mi> <m:mi>h</m:mi> </m:mrow> </m:msub> <m:mo>≤</m:mo> <m:mn>1</m:mn> </m:mrow> </m:math> ${n}_{ch}^{\left(c\right)}{< }{n}_{ch}\le 1$ , where <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:msub> <m:mi>n</m:mi> <m:mrow> <m:mi>c</m:mi> <m:mi>h</m:mi> </m:mrow> </m:msub> </m:mrow> </m:math> ${n}_{ch}$ is the ratio of isothermal cold and non-thermal hot electron number densities, and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:msubsup> <m:mi>n</m:mi> <m:mrow> <m:mi>c</m:mi> <m:mi>h</m:mi> </m:mrow> <m:mrow> <m:mo>(</m:mo> <m:mi>c</m:mi> <m:mo>)</m:mo> </m:mrow> </m:msubsup> </m:mrow> </m:math> ${n}_{ch}^{\left(c\right)}$ is a critical value of n ch . Also, we have seen that the amplitude of the positive potential solitons decreases with increasing β e , where β e is the non-thermal parameter. We have also investigated the transition of different negative potential solitary structures: negative potential soliton (before the formation of negative potential double layer) → negative potential double layer → negative potential supersoliton → negative potential soliton (after the formation of negative potential double layer) by considering the variation of θ only, where θ is angle between the direction of the external uniform static magnetic field and the direction of propagation of the ion acoustic wave.