Reflection of Solitons at Critical Density of Negative Ions: Contribution of Thermal and Gyratory Motions of Ions

Abstract

On the basis of appropriate modified KortewegdeVries (mKdV) equation derived for three cases of n n0 < n e0 , n n0 = n e0 , and n n0 > n e0 together with n n0 (n e0 ) as the density of negative ions (electrons), we observe that compressive and rarefactive mKdV solitons propagate in an inhomogeneous magnetized plasma having negative ions at their critical density. Two types of modes (fast and slow) separately evolve as the compressive and rarefactive solitons. However, only the solitons corresponding to the fast mode get reflected, if the obliqueness of the magnetic field lies under certain critical angle ψ CR which gets larger under higher thermal motions of the ions and shows stronger dependence on it when less number of negative ions are present in the plasma. There is a possibility of the change of polarities after the reflection of the solitons. The solitons suffer stronger reflection under the effect of larger ion thermal motions and smaller obliqueness of the magnetic field. The compressive solitons are found to downshift, whereas the rarefactive solitons are upshifted after the reflection, and these shifts get higher for the increasing concentration of the negative ions and lower obliqueness of the magnetic field. The compressive (rarefactive) solitons shift less (more) in the plasmas with ions of higher thermal energy; however, the upshift shows opposite behavior for the case of n n0 > n e0 .Index Terms-Compressive and rarefactive solitons, critical density, negative ions, soliton reflection, thermal and gyratory motions of ions.

Reflection of ion acoustic solitary waves in a dusty plasma with variable charge dust

“…However, the terms without sech 2 represent the shift of this structure. Consistent to the observation of earlier work [35], the soliton is found to be shifted after its reflection, and the shift amounts of the first two terms of RHS of Eq. (47), i.e.,…”

“…The occurrence of only the compressive solitons in the present plasma can be understood as follows. In negative ion containing plasmas, there exists a critical density of negative ions below which compressive solitons exist and above which rarefactive solitons propagate [34,35]. Since in the present plasma having negatively charged stationary dust grains there does not exist such critical density neither a and a R vanish nor carry negative values, only the compressive solitons are found to evolve.…”

Soliton reflection in a magnetized inhomogeneous warm plasma: effect of ionization

“…For this reason, lesser is the amount of energy of the incident soliton and hence, smaller is the amount of energy that is being used in shifting the soliton. Malik et al [31] had also observed that when the incident soliton is reflected strongly then the amplitude of reflected soliton and the reflection coefficient attain higher values. However, the shift was found to behave oppositely [31].…”

“…Malik et al [31] had also observed that when the incident soliton is reflected strongly then the amplitude of reflected soliton and the reflection coefficient attain higher values. However, the shift was found to behave oppositely [31]. In contrast to this, in the presence of ionization, the shift and reflection coefficients are found to behave consistently.…”

“…In addition to the above work, researchers have studied the propagation of solitary waves under the effect of magnetic field [26][27][28][29][30], where the modified characteristics of solitary waves were realized. Reflection of soliton was observed with weak density gradient by Malik et al [31]. Kumar et al [32] have studied the soliton reflection in a plasma with trapped electrons and dust grains.…”