Low-frequency Electrostatic Waves Research Articles

Coupled nonlinear drift and IAWs in streaming O–H plasma of upper ionosphere

Nonlinear structures formed by the coupled drift wave (DW) and ion acoustic waves (IAWs) are studied in a magnetized inhomogeneous collisionless bi-ion plasma with ions shear flow along the ambient magnetic field B=B0ẑ. The electrons are assumed to follow double spectral index (r, q) distribution in which r shows the flat top nature, while q is responsible for the shape of the distribution at the tail. A nonlinear differential equation is derived, and its solutions in the form of double layers (DLs) and solitons are obtained in different limits. It is pointed out that the presence of (0.4%) protons in the oxygen plasma of ionosphere should not be ignored because acoustic speeds corresponding to oxygen and hydrogen ions have small ratio of about four and drift wave frequency may lie in the same range. It is found that only the rarefactive solitons can be formed by the nonlinear DW and IAWs in the inhomogeneous oxygen hydrogen (O–H) plasma. However, the theoretical model predicts that both compressive and rarefactive DLs may be formed. The linear instabilities of low-frequency electrostatic waves due to field-aligned shear flow of ions have also been investigated.

Boundary effects on dispersion relations of ion-acoustic wave and physical properties of overlapping soliton in a plasma waveguide

Taking into account the cylindrical boundary, a theoretical investigation has been made for the low frequency electrostatic waves in an electron-positron-ion plasma waveguide. The dispersion relation of ion-acoustic (IA) wave is obtained, and a predication for the linear interaction phenomenon of small-amplitude cylindrical IA solitons is presented. It is shown that the cylindrical boundary has significant effects on the dispersion property of IA waves, and the frequency for short wave is significantly modified by the plasma parameters. It has also been noted that cylindrical IA solitons add up linearly when they overlap and penetrate through each other, the maximum amplitude of the overlapping soliton is nearly the sum of the individual soliton amplitude, indicating an apparent linear interaction. Furthermore, the relationships between phase delay and kinetic energy of colliding solitons for an axisymetric cylindrical geometry are derived and discussed in detail. The work presented would be useful to enrich the solitons interaction theory in astrophysical and laboratorial plasma situations.

Ion acoustic waves in lunar wake plasma

Kinetic theory of low frequency electrostatic waves is carried out in the lunar wake plasma modelled by kappa electrons, kappa-beam electrons, Maxwell–Boltzmann distributed protons and doubly charged Helium ions. The present work is motivated by observation of electrostatic waves on the outbound side of the first lunar wake flyby of the mission Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) probe P1. The dispersion characteristics of electrostatic waves which are identified as ion-acoustic waves are carried out for the observational plasma parameters. The frequencies of the ion acoustic waves derived from the model corresponding to peak growth rates are f⩽0.02fpe; (fpe being electron plasma frequency) which matches with the frequency of the waves observed by wave burst 1 (WB1) in the lunar wake (Tao et al., 2012). Our theoretical analysis reveals that in order to excite the low-frequency wave modes, low-energy electron beams are required which are not apparent in the observations.

Juno Plasma Wave Observations at Ganymede.

The Juno Waves instrument measured plasma waves associated with Ganymede's magnetosphere during its flyby on 7 June, day 158, 2021. Three distinct regions were identified including a wake, and nightside and dayside regions in the magnetosphere distinguished by their electron densities and associated variability. The magnetosphere includes electron cyclotron harmonic emissions including a band at the upper hybrid frequency, as well as whistler-mode chorus and hiss. These waves likely interact with energetic electrons in Ganymede's magnetosphere by pitch angle scattering and/or accelerating the electrons. The wake is accentuated by low-frequency turbulence and electrostatic solitary waves. Radio emissions observed before and after the flyby likely have their source in Ganymede's magnetosphere.

Ion temperature gradient mode and its solitons with regularized κ-distributed electrons

The linear and the non-linear behaviors of the ion temperature gradient (ITG) mode in a plasma with regularized κ-distributed electrons are investigated using the fluid model. The dispersion relation of the ITG mode obtained on the basis of the local approximation shows that the growth rate of the ITG mode decreases with the increase in the spectral index κ and the exponential cut-off parameter α. It indicates that the presence of the superthermal electron leads to destabilization of the ITG mode, especially in the low κ (κ < 1.5) region. In addition, the existence and the nature of the soliton structure driven by the ITG are studied using the pseudopotential technology. The soliton amplitude increases with the increase in the exponential cut-off parameter α and the spectral index κ, whereas the width of the soliton varies inversely. The present results will help to understand the low-frequency electrostatic wave and nonlinear structure in space and experimental plasmas with non-thermal electrons.

Coupling and Instability of Electrostatic Waves in Spin Magnetized Degenerate Plasmas

In this article, we study the coupling of low-frequency electrostatic waves in the electron-ion and the electron-ion-beam-spin quantum plasmas. The quantum effect of electrons are introduced via separate spin evolution-quantum hydrodynamic (SSE-QHD) model while the ion dynamics is governed by classical fluid equations. In the case of electron-ion plasma, it is found that the quantum effects shift both the coupling domain and the phase velocities of coupled waves. Furthermore, the coupling is observed to be strong at small propagation angles. In the beam interacting system, two coupling domains occur corresponding to small and large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> -values. In the first domain beam mode excites the ion cyclotron (IC) wave and moves with constant phase velocity while in the second domain it gains energy from the ion acoustic (IA) mode and travels with increasing phase velocity. In addition, the beam parameters affect both the coupling domain and the phase velocity. The presence of beam in electron-ion plasma drives the IC mode unstable. The beam parameters, the spin, and the obliqueness affect the instability. Our findings may be helpful in understanding the energy exchange of plasma waves via coupling phenomenon in degenerate plasma systems.

Theoretical studies of low and high frequency electrostatic solitary waves in the magnetopause associated with asymmetric magnetic reconnection

In a comprehensive analysis of Cluster data, Graham et al. (2015) have reported the existence of slow and fast electrostatic solitary waves (ESWs) associated with asymmetric magnetic reconnection arising from the merger of the magnetic fields, and mixing, of the hot tenuous magnetospheric plasma and the cooler dense magnetosheath plasma. Their analysis also reveals the presence of four electron species, two background Maxwellian distributions and a pair of counter-streaming electron beams. Using the measured plasma parameters and a plasma model consistent with the observations, together with an ion component for charge neutrality, we use fluid dynamic theory in an attempt to identify the plasma modes associated with the ESWs, as well as the polarity and admissible range in speed of the fast and slow structures. It can be inferred from the data sets in Figure 4 in Graham et al. (2015) obtained during the crossing of the Cluster satellites C3 and C4 of the separatrix near the ion diffusion region that the distributions of the two counterstreaming electron beams vary from having identical characteristics to showing small differences over the period during which the ESWs were observed. Accordingly, we align the theoretical parameters in our study with Cluster observations by considering the effect of identical and non-identical counterstreaming electron beam distributions on the existence of ESWs.

On the propagation of electrostatic wave modes in the inhomogeneous ionospheric plasma of Venus

The influence of gradients of number density, magnetic field, and flow velocity in a plasma on the propagation of low-frequency electrostatic waves is investigated in plasma conditions relevant for the Venusian ionosphere (vicinity of Venus terminator). For this purpose, we assume a collisionless inhomogeneous plasma model consisting of two positive ion species, hydrogen H+ and oxygen O+, as well as neutralizing electrons. Linear dispersion relations predict two types of plasma modes, namely, ion-acoustic mode and drift mode. It is found that these modes have relatively long wavelengths, extending to 10 km and frequencies on the order of ∼10−3−10−2 Hz. The characteristics of these modes show a strong dependence on the gradients of plasma parameters, and numerical analysis reveals that the coupling of these modes may lead to nonlinear instabilities. However, unstable modes occur only when the field-aligned shear flows are introduced. These results help explain the presence of low-frequency electrostatic modes and their basic features in the Venusian ionosphere, and will allow future studies to extend modeling to other planetary or even cometary conditions.

The effects of suprathermal particles on the existence domain of oblique low-frequency solitary waves in multi-component magnetospheric plasmas

The effect of suprathermal particles is examined on arbitrary amplitude nonlinear low-frequency electrostatic solitary waves propagating obliquely to the ambient magnetic field of the terrestrial magnetosphere using the Sagdeev pseudopotential formalism. The four-component plasma model consists of cold singly charged oxygen ions, hot protons, and two distinct groups of electrons with the latter three having kappa velocity distributions. Our numerical investigations based on comparatively low values for the spectral indices of the two electron species and the hot proton distributions as inferred from time history of events and macroscale interactions during substorms mission data reveal that the coexistence of compressive and rarefactive solitons is suppressed in comparison to the behavior in the presence of Maxwellian species (infinitely large values of kappa). Also, the existence of positive potential solitons is suppressed in an intermediate range of cold oxygen-ion densities. The differences are attributed to the occurrence of singularities in the Sagdeev potential for the chosen set of spectral indices.

Sticky islands in stochastic webs and anomalous chaotic cross-field particle transport by E×B electron drift instability

The ExB electron drift instability, present in many plasma devices, is an important agent in cross-field particle transport. In presence of a resulting low frequency electrostatic wave, the motion of a charged particle becomes chaotic and generates a stochastic web in phase space. We define a scaling exponent to characterise transport in phase space and we show that the transport is anomalous, of super-diffusive type. Given the values of the model parameters, the trajectories stick to different kinds of islands in phase space, and their different sticking time power-law statistics generate successive regimes of the super-diffusive transport.

Polarization force in an opposite polarity dusty plasma with hybrid Cairns–Tsallis distributed electrons

AbstractThe effect of polarization force acting on oppositely charged dust grains in magnetized plasma is analysed for obliquely propagating low frequency electrostatic waves with Maxwellian ions, and non‐Maxwellian electrons following the hybrid Cairns–Tsallis velocity distribution. It is shown that the polarization force acting on positively charged dust grain is different from the one acting on negatively charged dust grain in the presence of hybrid Cairns–Tsallis distributed electrons. A nonlinear equation in the form of Zakharov–Kuznetsov equation is derived via perturbation analysis for the description of electrostatic solitary structures in the limit of weak‐amplitude. A parametric investigation determines the modifications arising in the propagation of dust acoustic soliton due to the presence of polarization force and hybrid Cairns–Tsallis distributed electrons. It is also found that the effect of polarization force is more pronounced for heavier dust grain with high charge number. Finally, there is a lower limit found for the q‐nonextensive parameter, below which modifications in soliton profile cease to exist due to the presence of hybrid Cairns–Tsallis distributed electrons.

Ionospheric Outflow During the Substorm Growth Phase: THEMIS Observations of Oxygen Ions at the Plasma Sheet Boundary

AbstractIonospheric outflow is an important plasma source that feeds the near‐Earth magnetotail with heavy oxygen ions. Because these ions can significantly alter the structure and stability of the magnetotail current sheet, the characteristics of this outflow are important for accurate magnetosphere modeling, including modeling of substorms—a key element of magnetosphere dynamics. Using Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft measurements in the magnetotail (around the plasma sheet boundary), we investigate characteristics oxygen outflows observed during substorm growth phases. The observed oxygen ion temperature and flow energy indicate that the outflow is marginally stable to ion acoustic wave generation: The oxygen temperature is slightly lower than the electron temperature and slightly higher than the oxygen flow energy. Moreover, the observed outflows are accompanied by low frequency electrostatic waves that may contribute to outflow thermalization. The oxygen bulk velocity has a significant component directed toward the equatorial plane, originating from the cross‐field drift in the convection electric field. The estimated radial distances at which oxygen ions reach the plasma sheet are ∼20–40RE downtail, that is, outflows during substorm growth phases can alter current sheet characteristics around the potential magnetic reconnection region.

Kappa distributed trapped electrons, drift wave instability and nonlinear structures in O–H plasma of ionosphere

Generation of drift waves by field-aligned shear flow of protons and oxygen ions is investigated in the presence of kappa distributed trapped electrons in upper ionosphere within auroral latitudes. Very low-frequency electrostatic waves having frequencies of the order of a few Hz observed by Freja satellite at altitude 1700 km can be either the ion acoustic waves (IAWs) or the electrostatic drift waves EDW depending up on density uniformity or non-uniformity in the region. Growth rate of drift wave increases in the presence of 0.4 percent hydrogen ions in oxygen plasma. Drift wave is coupled with the four branches of ion acoustic modes in this bi-ion plasma. In nonlinear regime, EDW and IAWs produce electrostatic solitary structures of a few meters width and their amplitude depends up on the density gradient scale length, non-thermality parameter and trapping of electrons.

Propagation of ion-acoustic surface waves in a turbulent quantum plasma with quantum recoil: transverse truncation method approach

The effect of quantum recoil on the low-frequency electrostatic surface waves on a semi-bounded quantum turbulent plasma is investigated based on the kinetic dielectric permittivity of a plasma where the wave frequency is in the range of ion-acoustic wave. The dispersion relation and the damping rate of the surface wave are derived by employing the specular reflection boundary condition and the transverse truncation method. It is shown that the frequency of surface wave is enhanced by the quantum recoil for both non-degenerate and degenerate cases. The magnitude of damping rate is also increased by the quantum effect. The quantum recoil effect on the wave propagation is significantly reduced as the wave number becomes small. In the range of such small wave numbers, the diffusional dissipation becomes more important for the wave propagation.

Landau quantization effects on hybrid waves in semiconductor plasmas

The impact of Landau quantization on the lower hybrid waves (LHWs) exciting in the semiconductor plasmas, due to classical electron beam, is studied. The quantum hydrodynamic model is employed to derive the dispersion relation of low-frequency electrostatic waves for instability analysis of the LHWs. The quantum effects include Fermi degenerate pressure, Bohm potential, Landau quantization, and exchange-correlation potential for semiconductor plasma species. The dispersion relation is elaborated both quantitatively and qualitatively for the special case of GaAs in the presence of external magnetic field $$\mathbf{B}_0$$. The impact of different plasma parameters such as density ratios of electrons and holes $$\alpha $$, beam temperature $$T_{\mathrm{b}}$$, speed of beam electrons $$v_0$$, propagation angle $$\theta $$, cyclotron frequency $$\omega _{\mathrm{ce}}$$, temperature of electrons and holes $$T_{\mathrm{e}}$$, $$T_{\mathrm{h}}$$ and Landau quantization $$\eta $$, on the dispersion relation of LHWs, is studied. The instability of the LHWs remarkably increases by increasing the concentration of the semiconductor electrons, propagation angle of the wave vector and the beam speed, for the magnetic quantization parameter. However, the instability decreases by increasing the temperature of beam. It is noticed that at $$(T_{\mathrm{b}}>v_0)$$, the $$\eta $$ has no effect on the instability.

Radiative and gravitating modes in the partially ionized magnetized dusty plasma

In the present study, fluid theory is used to investigate the gravitational and radiative condensation instabilities of a partially ionized magnetized dusty plasma system. The effects of ion and electron capture by dust grains, the charge variation of dust grains, and the radiative effects of electron species are also taken into account. The dynamics of all four species are considered to derive modified densities that further lead to a general dispersion relation. The general dispersion relation describes the propagation of low frequency electrostatic dust acoustic waves in magnetized self-gravitating partially ionized dusty plasma with ionization-recombination, dust charge variations, and radiative effects. Gravitational modes of propagation and radiative modes of propagation are illustrated separately for both parallel and perpendicular cases. Conditions for instabilities are also derived to explain the gravitational collapse and radiative condensation of the system. The numerical results are presented to signify the role of dust neutral collision frequency, dust charge fluctuation, magnetic field, and recombination ionization effects on both the radiative condensation and gravitational instabilities. The relevance of the present study to interstellar molecular clouds is also discussed and the effect of considered parameters on the critical wavelength, critical wave number, luminosity, etc., has been investigated.

Electrostatic solitary structures in warm multi-ion dusty plasmas: The effect of an external magnetic field and nonthermal electrons

Adopting a multi-fluid dynamical approach, the propagation of weakly nonlinear electrostatic solitary waves in a warm multi-ion dust plasma is investigated. In particular, a plasma is composed of positively and negatively charged ions and positively or negatively charged dust in the presence of superthermal electrons immersed in an external magnetic field. In the linear regime, two modes exist, namely, the slow and fast ion-acoustic modes. Employing the reductive perturbation technique, the governing equation of the nonlinear propagation for the electrostatic solitary pulse is derived. The polarity and structural characteristics (amplitude and width) of the localized electrostatic pulse in the plasma are thus analyzed for various values of relevant plasma configurations, namely, the degree of the superthermality (κ), the magnetic field strength Ωj, and the adiabatic ion thermal pressure coefficient σj. Our investigations should be useful to better understand the characteristics of the low-frequency electrostatic solitary wave that are ubiquitous in the laboratory and space plasmas, where a warm dusty multi-ion plasma with the energetic (suprathermal) electrons exists and an external magnetic field is included.

Estimation of Growth Rate of Electromagnetic Plasma Wave through Vlasov-Maxwell Mathematical Frame in Ionospheric Plasma

Unique forms of nonlinear wave energy exchange phenomena are observed in the Earth’sionosphere region. Energy upconversion of nonresonant plasma waves in the top ionospheric and auroral zone are noticed.Origin of these phenomena are tried to explained by linear andnonlinear theoretical approach.Wave-wave and wave-particle-wave interaction processes may be possible role takes place here.In this theoretical investigation we wish to derive probable growthrate expression of high frequency electromagnetic O-mode wave in the presence of low frequency electrostatic ion sound wave through wave-particle interaction process known as plasma maserinstability and estimate its value by using observational data.

Obliquely propagating low-frequency magnetospheric electrostatic solitary waves in the presence of an oxygen-ion beam

Nonlinear propagation of finite amplitude low-frequency electrostatic solitary waves is examined in a magnetized three-component plasma consisting of a cold singly-charged oxygen-ion beam and Boltzmann distributed background protons and electrons. The theoretical analysis is carried out by assuming the charge neutrality condition at equilibrium. Using parameters determined from satellite observation data for the magnetopause and plasma sheet regions of the Earth’s magnetosphere, the model shows the existence of positive polarity soliton structures with amplitudes that decrease as the obliquity of the wave propagation increases.

Current-Driven Low-Frequency Electrostatic Waves in a Collisional Strongly Coupled Magnetized Dusty Plasma

Current-driven low-frequency electrostatic waves are studied in a collisional strongly coupled magnetized dusty plasma. The theoretical model for the longitudinal and transverse modes is developed in the regime $\omega \tau _{m} \ll 1$ for the collisional strongly coupled magnetized dusty plasma in the presence of drifting currents. It is observed that the dispersion properties of low-frequency electrostatic waves are modified under the effect of magnetic field-aligned drifting ion currents in a strongly coupled collisional magnetized dusty plasma. The frequency rate and growth rate of longitudinal and transverse modes increase with normalized wave number. Moreover, the growth rate of unstable waves is destabilized with normalized drift velocity of ions for both longitudinal and transverse modes. The critical drift velocity of ions decreases with normalized wave number but increases with increase in the strong correlation parameter $\Gamma $ . The effect of strong coupling parameter on the frequency and growth rate of low-frequency electrostatic modes in the presence of current drift and collisions is also investigated.