Speaker
Ashesh Paul
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.3011.pdf
Dust ion acoustic solitary structures at the acoustic speed in presence of
nonthermally distributed electrons and positrons
Ashesh Paul1 and Anup Bandyopadhyay 1
1
Jadavpur University, Kolkata, India
The Sagdeev pseudo-potential technique and the analytic theory developed by Das et al. [1]
have been used to investigate the dust ion acoustic solitary structures at the acoustic speed in
a collisionless unmagnetized dusty plasma consisting of negatively charged static dust
grains, adiabatic warm ions, Cairns [2] distributed nonthermal electrons and positrons.
Several authors investigated small or arbitrary amplitude dust ion acoustic solitary structures
in different electron-positron-ion-dust plasma systems. But in all those works dust ion
acoustic solitary structures have been considered at the supersonic speed only, i.e., for
𝑈 > 𝐶𝐷 , where 𝑈 is the velocity of the wave frame and 𝐶𝐷 is the linearized velocity of the
dust ion acoustic wave for long wave length plane wave perturbation. In the present paper,
we have studied the dust ion acoustic solitary structures at the acoustic speed i.e., for 𝑈 = 𝐶𝐷
with the help of the existence domains and the phase portraits of the dynamical system
describing the nonlinear behaviour of the dust ion acoustic waves in the same plasma system
considered by Paul et al. [3]. At the acoustic speed, the system supports both positive and
negative potential solitary waves, but does not support the coexistence of solitary waves of
opposite polarities. The system also supports negative potential double layer at the acoustic
speed, but does not support positive potential double layer. Although the system supports
positive potential supersoliton at the supersonic speed, but there does not exist supersoliton
of any polarity at the acoustic speed. For the first time, we have introduced the phase portrait
analysis of the dynamical system corresponding to the solitary structures at the acoustic
speed. Phase portraits of the dynamical system corresponding to different dust ion acoustic
solitary structures indicate the difference between the solitary structures at the acoustic speed
( 𝑈 = 𝐶𝐷 ⇔ 𝑀 = 𝑀𝐶 ) and the solitary structures at the supersonic speed ( 𝑈 > 𝐶𝐷 ⇔
𝑀 > 𝑀𝐶 ).
References:
[1] A. Das, A. Bandyopadhyay, and K. P. Das, J. Plasma Phys. 78, 565 (2012).
[2] R. A. Cairns, A. A. Mamun, R. Bingham, R. O. Dendy, R. Bostrӧm, P. K. Shukla, and C. M. C. Nairn,
Geophys. Res. Lett. 22, 2709 (1995).
[3] A. Paul, A. Bandyopadhyay, and K. P. Das, Phys. Plasmas 24, 013707 (2017).
