Beam-Generated Collisionless Ion-Acoustic Shocks

Abstract

A numerical study of a one-dimensional collisionless ion-acoustic shock generated by an injection of a plasma beam is presented. The electrons are assumed to be hot and isothermal, and obey the Boltzmann distribution; the ions are described by the Vlasov equation which is solved by a direct finite difference scheme. There is a threshold beam velocity ubm, above which shock is not generated. ubm is a function of the beam-background density ratio and the electron-ion temperature ratio, and is larger than the limit of the ion-ion two-stream instability uts. For beam velocities ranging from zero to uts a shock is observed followed by a region of fully developed two-stream instability. For beam velocities between uts and ubm, a shock and a phase-space vortex are formed and in between them a quiescent region grows. A stable two-stream remains behind the vortex.

Phase space vortices in collisionless plasmas

“…2 dealt with phenomena on short time scales, where the ion component could be considered immobile. Similar vortical structures were found numerically (Sakanaka, 1972; and experimentally (Pécseli et al, 1981) also in ion phase space, where now both electron and ion components participate in the plasma dynamics. In the experiments on ion phase space vortices, the evolution of the ion distribution function, and thereby, the phase space dynamics, could be measured directly by an ion energy analyzer (see also a summary by .…”

“…10, we note a temperature increase associated with the shock, and also here, we see some of the background ions being trapped in the phase space vortices. The phase space vortices form in the linearly, unstable ion-ion stream region behind the shock (Sakanaka, 1972;Pécseli and Trulsen, 1982;. A typical width of the vortices is approximately 15λ Di ≈ 5λ De , i.e.…”

Phase space structures generated by absorbing obstacles in streaming plasmas

“…The conspicuous features of the potential structures seem to be associated with phase space vortices, where all the relevant dynamics seem to take place in {x, v x }-plane, as expected for potential structures elongated in the y-direction, as here. Such ion phase space vortices are well-known, and have been observed experimentally by Pécseli et al (1981Pécseli et al ( , 1984, as well as in a number of numerical simulations (Sakanaka, 1972;Børve et al, 2001;Daldorff et al, 2001;. In particular, the coalescence seen in Fig.…”

Dust ion-acoustic solitary waves in a dusty plasma with arbitrarily charged dust and flat-trapped electrons

“…It has been shown by Rosenberg and Mendis (1995) that as a result of only the photoemission process a dust grain of few micron size can acquire a positive charge of the order of 10 2 -10 5 proton charges. On the other hand, computer simulations and laboratory observations indicate the presence of trapped electrons during the low frequency electrostatic wave evolution (Sakanaka 1972;Saeki et al 1979). It is well known that such electron distribution modifies the conditions for the existence of nonlinear waves associated with the DIA waves, particularly the DIA solitary and shock waves which are not observed in dusty plasma with isothermal electrons (Schamel 1972(Schamel , 1979Popel et al 2003;Duha et al 2010;Alinejad and Tribeche 2010).…”