[1] A parametric study of high-frequency nonlinear electrostatic oscillations in a magnetized plasma consisting of hot electrons, cool electrons, and cool ions has been conducted. The fluid equations have been used for each species, and the coupled system of differential equations in the rest frame of the propagating wave have been numerically solved to yield the electric field for parameters characteristic of the auroral region. The effect of the initial driving amplitude, cold and hot electron densities, propagation angle, hot electron drift, and cool electron and cool ion temperatures on the electric field structures have been investigated and, in particular, the frequency and the type of electric field structure (sinusoidal, sawtooth, or spiky). The initial driving amplitude as well as the cold and hot electron densities are shown to affect the nature (sinusoidal, sawtooth, or spiky) of the waveforms, with a transition from linear sinusoidal waveforms for low initial driving amplitude, to spiky, nonlinear waveforms for larger values of the initial driving amplitude. In addition, the drifts of the species are shown to play a crucial role in the periods of the waveforms, while the temperatures of the electron species are also shown to vary the periods of the waveforms but not as much as in the case of the drifts of the species. The results show a strong resemblance to satellite observations of the different types of broadband electrostatic noise reported, which are nonlinear, spiky structures of varying amplitude and period.
Observations from the Fast Auroral SnapshoT (FAST) satellite indicate that the parallel and perpendicular (to the Earth’s magnetic field) electric field structures exhibit a spiky appearance. In this study, a magnetized plasma system consisting of protons, electrons, and a cold oxygen ion beam is considered. Both background electrons and protons are treated as hot species with Boltzmann density distributions. The dynamics of the oxygen ion beam is governed by the fluid equations. Effect of charge separation is studied on nonlinear fluctuations arising from a coupling of ion cyclotron and ion-acoustic waves. A scan of parameter space reveals a range of solutions for the parallel electric field from sinusoidal to sawtooth to highly spiky waveforms. The inclusion of charge separation effects tends to in most cases increase the frequency of oscillation of the nonlinear structures. In the case of a weakly magnetized plasma, the amplitude of the oscillations are found to be constant while they are modulated for a strongly magnetized plasma. The findings are compared with satellite observations.
The generation of nonlinear electrostatic solitary waves (ESWs) is explored in a magnetized four component two-temperature electron–positron plasma. Fluid theory is used to derive a set of nonlinear equations for the ESWs, which propagate obliquely to an external magnetic field. The electric field structures are examined for various plasma parameters and are shown to yield sinusoidal, sawtooth and bipolar waveforms. It is found that an increase in the densities of the electrons and positrons strengthen the nonlinearity while the periodicity and nonlinearity of the wave increases as the cool-to-hot temperature ratio increases. Our results could be useful in understanding nonlinear propagation of waves in astrophysical environments and related laboratory experiments.
Analytical linear electrostatic waves in a magnetized three-component electron-positron-ion plasma are studied in the low-frequency limit. By using the continuity and momentum equations with Poisson's equation, the dispersion relation for the electron-positron-ion plasma consisting of cool ions, and hot Boltzmann electrons and positrons is derived. In the linear regime, the propagation of two possible modes and their evolution are studied. In the cases of parallel and perpendicular propagation, it is shown that these two possible modes are always stable. The present investigation contributes to nonlinear propagation of electrostatic waves in space and the laboratory.
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