On the role of suprathermal electrons on the characteristics of electrostatic solitary waves in Saturn’s magnetosphere (original) (raw)
Related papers
2022
Over the past few decades, a range of theoretical models and experiments have provided ample evidence for the occurrence of kappa distributions in various space plasma environments, including the solar wind, planetary magnetospheres, the outer heliosphere, and the inner heliosheath. Among various planetary magnetospheres, Saturn's magnetosphere, for one, makes an excellent testing ground for the investigation of kappa-distributed electrons. Suprathermal electron populations may play a decisive role in the generation of plasma waves in Saturn's magnetosphere plasma. The Cassini spacecraft mission has detected Electrostatic Solitary Waves (ESWs) in Saturn's magnetosphere. Motivated by this fact and by observations of suprathermal electrons on Saturn, we have formulated a theoretical model to explore the significance of the electron parameters (density, temperature) in the evolution and the characteristics of ESWs occurring in Saturn's magnetosphere. Our method provides an efficient tool for understanding ESWs and their dependence on electron statistics, which may be vital in characterizing the microphysics of Saturn's magnetosphere.
Research Square (Research Square), 2022
The linear and nonlinear propagation characteristics of dust ion acoustic waves (DIAWs) are investigated in a collisionless, magnetized dusty plasma. The system is composed of (r; q) distributed electrons with warm ions and stationary dust and propagation of wave is taken in x-z plane. The linear properties of the system are studied for the plasma parameters of Saturn magnetosphere are studied by the dispersion relation. The characteristics of oblique propagation of dust ion acoustic solitary waves (DIASWs) are studied by deriving Korteweg de Vries (KdV) equation and the critical point is determined at which the nature of solitons changes. The in ‡uence of various parameters, namely, obliqueness, magnetic …eld, densities, temperatures and spectral indices of the (r; q) distributed electrons on DIASWs is investigated for Saturn's magnetosphere. The DIASWs of (r; q) distributed electrons are also compared with Maxwellian electrons. The present work might be helpful to study other astrophysical and laboratory plasma systems where dusty plasmas and (r; q) distribution are predicted.
Monthly Notices of the Royal Astronomical Society, 2019
Thanks to the evidence provided by the Cassini spacecraft mission, it is now established that Saturn's magnetospheric plasma consists of various types of positive ions, as well as two distinct populations of electrons, at different temperatures. The electron population energy distributions are characterized by long suprathermal tails and have been effectively modelled by kappa-type distributions. Plasma properties are known to vary along the radial direction. A strong magnetic field penetrates the magnetosphere, hence the plasma beta is small, β < 1 for radial distance < 15.2 R S (where R S = 60 330 km is the Saturn's radius). Motivated by these observations, we have investigated the conditions for existence and the dynamics of linear and non-linear kinetic Alfvén waves (KAWs) in Saturn's magnetosphere. We have considered a low-β (strongly magnetized) plasma, comprising of positive ions and two electron populations ('cold' and 'hot') characterized by non-Maxwellian (kappa) distributions. In the small-amplitude regime, harmonic analysis leads to a linear dispersion relation bearing explicit dependence on the characteristics of the suprathermal components. In the nonlinear regime, large-amplitude stationary profile kinetic Alfvén solitary wave solutions are obtained via a two-component pseudopotential method, associated with either positive or negative potential structures (pulses) propagating at sub-and super-Alfvénic speeds, respectively. The effect of various intrinsic plasma configuration properties (hot-to-cold electron density and temperature ratio; superthermality indices κ c and κ h ; plasma beta) as well as propagation parameters (pulse speed, direction of propagation) on the characteristics of KAW solitary waves are discussed.
Electrostatic Solitary Waves in Electronegative Martian Plasma
The Astrophysical Journal, 2024
The solar wind interacts with planetary magnetospheres, generating plasma waves in both the upstream region and the magnetospheric environment. Mars, lacking an inherent magnetic field, has an induced magnetosphere formed through solar wind interaction with its ionosphere. These waves are crucial for momentum and energy exchange within the planetary plasma environment. This study focuses on the existence and dynamics of electrostatic solitary waves (ESWs) in Martian ionospheric plasma, characterized by various flowing ions. We employ a multifluid plasma model incorporating positive (streaming) ions, negative ions, and two distinct kappa-distributed electron populations to study ESW propagation in the Martian ionosphere from first principles. Linear analysis reveals four distinct modes, including a subsonic mode due to the negative-ion beam. Electrostatic waves may become unstable due to a beam instability excited at long wavelengths. Seeking stationary profile solutions, an energy balance equation is obtained in the moving reference frame, and the shape of the solitary wave can thus be predicted numerically. A meticulous analysis reveals that either positive-or negative-polarity ESWs (or both) may occur (simultaneously) in the Martian environment. In addition to conventional bipolar E-field waveforms, our theoretical model predicts the existence of wiggly bipolar pulses (supersolitary waves) and offset bipolar pulses (flat-top solitary waves) in Martian plasma. Comparison of our model's predictions with real observational plasma parameters indicates that, like Martian magnetosheath plasma, ionospheric plasma may sustain ESWs measuring several tens of millivolts per meter.
Particle in Cell Simulations of Electrostatic Waves in Saturn's Magnetosphere
2012
The characteristics of electrostatic waves are investigated using PIC simulations of a four component plasma: cool and hot electrons, cool ions and an electron beam. The velocities are defined by Maxwellian distributions. The system is one dimensional and simulates a collisionless, unmagnetized plasma. Langmuir waves, electron acoustic waves, beam-driven waves and ion acoustic waves are excited in the simulations. The results are analysed using the dispersion relation and compared with previous investigations and analytical results.
Plasma Physics Reports, 2020
We have investigated the propagation characteristics of Ion-Acoustic Solitary Waves (IASWs) in a magnetized, cometary plasma consisting of hydrogen ions, positively and negatively charged oxygen ions, kappa described hot solar electrons, and slightly colder cometary electrons. The effects of q-nonextensive distributions, on both lighter and heavier ions have been studied by deriving the Zakharov-Kuznetsov (ZK) equation. The basic features of IASWs such as amplitude, width, and phase speed have been extensively studied by a numerical analysis of the ZK equation. It is found that superthermality of the electrons and nonextensivity of ions significantly modify the characteristics of the solitary waves. The amplitudes of the solitary waves seem to be well correlated to the presence of water molecules in a cometary plasma and the associated photoionization processes.
Electron acoustic nonlinear structures in planetary magnetospheres
Physics of Plasmas, 2018
In this paper, we have studied linear and nonlinear propagation of electron acoustic waves (EAWs) comprising cold and hot populations in which the ions form the neutralizing background. The hot electrons have been assumed to follow the generalized ðr; qÞ distribution which has the advantage that it mimics most of the distribution functions observed in space plasmas. Interestingly, it has been found that unlike Maxwellian and kappa distributions, the electron acoustic waves admit not only rarefactive structures but also allow the formation of compressive solitary structures for generalized ðr; qÞ distribution. It has been found that the flatness parameter r, tail parameter q, and the nonlinear propagation velocity u affect the propagation characteristics of nonlinear EAWs. Using the plasmas parameters, typically found in Saturn's magnetosphere and the Earth's auroral region, where two populations of electrons and electron acoustic solitary waves (EASWs) have been observed, we have given an estimate of the scale lengths over which these nonlinear waves are expected to form and how the size of these structures would vary with the change in the shape of the distribution function and with the change of the plasma parameters.
Plasma wave measurements in the magnetosphere of Uranus
Journal of Geophysical Research, 1987
As Voyager 2 traversed the magnetosphere of Uranus, the plasma wave instrument detected very significant phenomena related to local wave-particle interactions, radio emissions, and dust impacts.