Weakly nonlinear ion waves in striated electron temperatures

Abstract

The existence of low-frequency waveguide modes of electrostatic ion acoustic waves is demonstrated in magnetized plasmas for cases where the electron temperature is striated along magnetic field lines. For low frequencies, the temperature striation acts as waveguide that supports a trapped mode. For conditions where the ion cyclotron frequency is below the ion plasma frequency we find a dispersion relation having also a radiative frequency band, where waves can escape from the striation. Arguments for the formation and propagation of an equivalent of electrostatic shocks are presented and demonstrated numerically for these conditions. The shock represents here a balance between an external energy input maintained by ion injection and a dissipation mechanism in the form of energy leakage of the harmonics generated by nonlinear wave steepening. This is a reversible form for energy loss that can replace the time-irreversible losses in a standard Burgers equation.

Weakly nonlinear ion sound waves in gravitational systems

“…In this limit (10) will be relevant, and the expression is implemented in our Particle in Cell (PIC) code. Details of the code are described elsewhere [5,28].…”

“…A generalization to a fully 3 dimensional system will in our case not bring any new features to is related to studies of weakly nonlinear electrostatic Trivelpiece-Gould modes in a magnetized plasma wave-guide [29]. Details of the analytical model used here are given elsewhere [5]. The basic analysis gives an equation for "simple waves" [30], which is subsequently generalized by introducing dispersion and the effect of gravity to give a modified Korteweg-de Vries equation.…”

“…Two limiting cases can be recognized: Ω ci > Ω pi and Ω ci < Ω pi in terms of ion cyclotron and ion plasma frequencies. A previous study [5] discussed weakly nonlinear ion waves for Ω ci < Ω pi . The other limit will be relevancy for the present analysis.…”

“…The waveforms analyzed in the following belong to the low frequency branch. A spatially one dimensional study is justified by considering conditions where a waveguide mode excited in a magnetic flux tube with enhanced electron temperatures, T ≫ T i compared to the surrounding plasma similar to a previous study [5].…”

Transport properties of a hollow pressure filament in a magnetized plasma

“…The nose of the heated filament acts as a piston that produces a collimated density pulse reminiscent of the ion-acoustic waveguide investigated by Guio and Pecseli. 23 panel ( Fig. 3(a)) shows the time evolution for a range of axial positions (2-10 m) at a fixed radial position r ¼ 2.5 cm, corresponding to the peak of the heated ring.…”