The experiments on solitons in plasmas performed during the period 1970 to 1982 are reviewed. Suggestions for future experiments are presented.

https://iopscience.iop.org/article/10.1088/0032-1028/25/9/001/pdf

Soliton experiments in plasmas

Plasma surface waves were discovered in 1958. The experiments done since then on these waves are critically reviewed and analysed in terms of appropriate models and corresponding dispersion relations. Discrepancies and unresolved issues are identified and discussed. Wave damping experiments and analysis, and results of more recent works on nonlinear aspects of these waves, are also reported.

https://iopscience.iop.org/article/10.1088/0032-1028/24/11/001/pdf

Experimental investigations of the propagation of surface waves along a plasma column

Experiments on the propagation and collision of a Korteweg–deVries soliton in a positive ion–negative ion plasma are described. Both a one‐dimensional overtaking collision and a two‐dimensional resonant collision are examined. Soliton propagation into a steady‐state plasma sheath created by an additional biased metal plate in such a plasma is large enough that the detailed soliton motion in the locally inhomogeneous plasma can be easily studied. A partial reflection and partial transmission of the soliton at a critical density within the sheath is observed and interpreted.

Soliton propagation, collision, and reflection at a sheath in a positive ion–negative ion plasma

Experimental observations on the partial reflection of a planar ion‐acoustic soliton from a plane rigid boundary with sharp density gradients are presented. The reflected wave attenuates rapidly, forming a spherical wave front apart from a small reflector. The reflection coefficient of about 25% at the boundary has no apparent dependence on the incident wave amplitude and the sheath thickness in front of the reflector in the case of the disk reflector, while it has a dependence in the case of the mesh reflector, having even larger values of up to about 50%.

Reflection of a planar ion‐acoustic soliton from a finite plane boundary

The review is concerned with wave propagation in plasmas where collisions may be neglected. The relevant kinetic theory is described by the Vlasov equation. Waves in the absence of a magnetic field are reviewed including Landau damping of electron waves and ion acoustic waves. The complications due to purely ballistic effects are described and the latter case includes the study of mixtures of ions. Thermal motion has little effect on electromagnetic waves with the exception of the anomalous skin effect. Beam-plasma interactions are reviewed and general concepts of stability are discussed. The conversion of wave energy from one kind of wave and linear coupling mechanisms are described. The importance of resonance cones is also noted.

https://iopscience.iop.org/article/10.1088/0034-4885/40/11/002/pdf

Waves and microinstabilities in plasmas-linear effects

The experimental observation of the reflection of ion acoustic waves from a negatively biased grid immersed in a plasma is reported. Reflection is detected only in the region where the plasma is “perturbed.”

Ion wave reflections as observed in a perturbed plasma.

Reviews four experimentally measured properties of waves which propagate in a medium having a dispersion relation D(k,ω)=1-ω02/ω2+k02/k2=0 where ω0 and k0 are characteristics of the medium. A transmission line, ion acoustic waves and electron plasma waves are examined and some similarity is found in their properties.

S. Aksornkitti

Papers

Ion wave reflections as observed in a perturbed plasma.

Properties of plasma waves defined by the dispersion relation

Dispersive‐like Properties of Accelerated Ion Bursts in a Plasma