Formation of Ion Phase-Space Vortexes

Abstract

The formation of ion phase space vortexes in the ion two stream region behind electrostatic ion acoustic shocks are observed in a laboratory experiment. A detailed analysis demonstrates that the evolution of such vortexes is associated with ion-ion beam instabilities and a nonlinear equation for their initial evolution is derived. The results are supported by a numerical particle simulation. Also the possibility of vortex excitation by ion bursts and coalescence of two vortexes are demonstrated. The effects of finite ion temperature, particle trapping and charge exchange collisions are discussed and the results related to ionospheric observations.

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.…”

“…There are not the same particles which constitute a structure at all times. Studies of the lifetime of ion phase space vortices (Pécseli et al, 1984;Børve et al, 2001) refer to initial value problems, and do not apply for the present case. If ion phase space vortices were to be analyzed as initial value problems with these plasma parameters, the resulting structures would appear as transient phenomena.…”

Nonlinearly generated plasma waves as a model for enhanced ion acoustic lines in the ionosphere

“…Although we note a strong activity also in ion phase space, we find it interesting that no ion holes are formed. The numerical results of Pécseli et al [1984] would indeed indicate that no such ion holes should be present, but as already mentioned, these observations refer to a case without electron plasma wave activity.…”

“…In our first attempt to explain this feature we considered the possibility of excitation of ion phase-space vortices, or ion holes. These BGK-type structures are well known from laboratory experiments and numerical simulations [Pécseli et al, 1984]. It has been found, however, that excitation of ion holes is ineffective when the electron/ion temperature ratio is below two [Pécseli et al, 1984], and this is after all the most common parameter range for many ionospheric conditions.…”

“…These BGK-type structures are well known from laboratory experiments and numerical simulations [Pécseli et al, 1984]. It has been found, however, that excitation of ion holes is ineffective when the electron/ion temperature ratio is below two [Pécseli et al, 1984], and this is after all the most common parameter range for many ionospheric conditions. Analytical and numerical studies by Shukla and Eliasson [2003] have demonstrated that ion phase space holes can be maintained by an enhanced level of Langmuir waves even for moderate ratios T e /T i .…”