Reflection of modified Korteweg–de Vries solitons in a negative ion plasma

Kawata

2007

Physics of Plasmas

Section: Discussion and Resultssupporting

confidence: 52%

Soliton propagation in an inhomogeneous plasma at critical density of negative ions: Effects of gyratory and thermal motions of ions

Kawata

2007

Physics of Plasmas

“…Interestingly, the first term in the right hand side of (19) causes the base of the reflected soliton to shift either upward or downward, the magnitude of which depends upon the peak amplitude of the incident soliton as well as on the other parameters in the plasma. Here, it is worth mentioning the observation of Yi et al [22] in an unmagnetized plasma that both the compressive and rarefactive solitons are reflected without shift and the polarity also remains the same after their reflection. Therefore, the two observations emphasize the difference made by the thermal motions of the ions and the magnetic field in the plasma.…”

Section: Coupling Of Mkdv Equations and Reflected Solitonsmentioning

confidence: 91%

“…The interesting property of the solitons is that they get reflected from the density gradient present in the inhomogeneous plasmas [16]- [21]. Their reflection has been investigated experimentally in negative-ion-containing plasmas [4], [22], [23] and in nonnegative ion plasmas [16]- [19], [24]. Also, a large number of studies have been carried out by theoretical researchers in this direction [9], [10], [20], [21], [25], [26].…”

Section: Reflection Of Solitons At Critical Density Of Negativementioning

confidence: 97%

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

IEEE Trans. Plasma Sci.

Singh²,

Kawata³

et al. 2008

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.

“…In addition to the soliton reflection in ordinary plasmas, the propagation of ion acoustic solitons [16][17][18][19] and their reflection [20][21][22][23] in an unmagnetized inhomogeneous plasma having both the positive and negative ions has been reported. For studying the soliton reflection problem theoretically, modified KdV equations for incident and reflected solitons were derived using the reductive perturbation analysis and then solved after their coupling.…”

Section: Introductionmentioning

confidence: 99%

Soliton reflection in a negative ion containing plasma: Effect of magnetic field and ion temperature

Singh

2006

Physics of Plasmas

Considering an inhomogeneous plasma having negative ions, positive ions, and electrons, relevant modified Korteweg-de Vries equations are derived and solved for obtaining the expressions of amplitudes and widths of the incident and reflected solitons together with the reflection coefficient under the combined effect of magnetic field, obliqueness (angle θ between the magnetic field and the direction of wave propagation) and ion temperature. A limit is found on the obliqueness θ for the reflection of incident soliton, which shows a dependence on the density, temperature, and drift velocity of both the ions. The incident solitons are observed to reflect more strongly under the effects of weak magnetic field, higher negative ion density, higher ion temperature, stronger density gradient and smaller angle θ. It is inferred that whereas the incident solitons show faster change in their characteristics with the ion density, the reflected solitons are more sensitive to the ion temperature.