New parametric decays of proton beam–plasma electromagnetic waves

Abstract

[1] Ion beam-plasma interactions are the source of wave activity in several space environments. Therefore the study of these waves and their parametric decays are very important in space physics. Thus we study parametric decays of right-hand polarized proton beam-plasma waves including the effect of the beam. It is shown that there are new instabilities due to the beam and the associated ion acoustic waves. The branch of the linear dispersion relation corresponding to the beam has negative energy so that whenever this branch participates in a decay, the corresponding instability should lead to an explosive instability. Some explosive behavior has indeed been found in simulation results involving right-hand polarized waves. Since the free-energy source of the linear beamplasma instabilities is the beam energy, one expects the beam speed to decrease as the waves grow and experience nonlinear decays. Therefore we study the effect of varying beam velocity in the parametric decays. It is shown that there are instabilities which depend on the beam velocity in such a way that they are stabilized as the beam decelerates.

Behavior of linear beam-plasma instabilities in the presence of finite amplitude circularly polarized waves

“…(5), are invariant under a rotation through an angle of 180 o . Therefore, it is sufficient to analyze the solutions in the upper half ω − k plane [9,10,20,14,15,16]. Note that for A = 0, only the ion-acoustic modes depend on the temperature.…”

“…The effect and the evolution of the beam for right and left handed polarized waves, have also been studied by using simulation experiments [17]. These studies have considered linearly stable systems [9,10,14,15,16]. Proton beams observed in the solar wind display large drift velocities which can be larger than the necessary velocity to generate a linear beam-plasma instability [18].…”

“…Their nonlinear evolution has also been studied by using drift kinetic effects [12] and hybrid computer simulation techniques [13]. Studies have been carried out by [14,15,16], including the effects of dissipation and of the beam drift speed. The effect and the evolution of the beam for right and left handed polarized waves, have also been studied by using simulation experiments [17].…”

Nonlinear ion‐acoustic waves supported by an ion beam

“…Assuming that each plasma species satisfies the fluid equations, and following a procedure similar to the work of Hollweg et al [1993] [see also, Jayanti and Hollweg , 1994; Gomberoff et al , 1994; Gomberoff et al , 1995a, 1995b; Gomberoff , 1995; Gomberoff et al , 2002; Gomberoff , 2003], the nonlinear dispersion relation can be written in the following form, …”

Parametric instabilities in magnetized multicomponent plasmas

“…It is worth noting that in other types of parametric problems, such as modulational and beam instabilities, a graphical approach is useful in classifying the instabilities; they occur where two normal mode lines cross and reconnect [29,30]. In those cases the number of interacting modes is finite, and the nonlinear dispersion relation can be obtained in closed form.…”