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Solar type V radio bursts are associated with type III bursts. Several processes have been proposed to interpret the association, electron distribution, and emission. We present the observation of a unique type V event observed by e-CALLISTO on 7 May 2021. The type V radio emission follows a group of U bursts. Unlike the unpolarized U bursts, the type V burst is circularly polarized, leaving room for a different emission process. Its starting edge drifts to higher frequency four times slower than the descending branch of the associated U burst. The type V processes seem to be ruled by electrons of lower energy. The observations conform to a coherent scenario where a dense electron beam drives the two-stream instability (causing type III emission) and, in the nonlinear stage, becomes unstable to another instability, previously known as the electron firehose instability (EFI). The secondary instability scatters some beam electrons into velocities perpendicular to the magnetic field and produces, after particle loss, a trapped distribution prone to electron cyclotron masering (ECM). A reduction in beaming and the formation of an isotropic halo are predicted for electron beams continuing to interplanetary space, possibly observable by Parker Solar Probe and Solar Orbiter. [ABSTRACT FROM AUTHOR]

The dynamics of strongly interacting particles are governed by Yang–Mills (Y–M) theory, which is a natural generalization of Maxwell Electrodynamics (ED). Its quantized version is known as quantum chromodynamics (QCD) (Gross and Wilczek, 1973; Politzer, 1973; ’t Hooft, 1972[1–3]) and has been very well studied. Classical Y–M theory is proving to be equally interesting because of the central role it plays in describing the physics of quark–gluon plasma (QGP) — which was prevalent in the early universe and is also produced in relativistic heavy ion collision experiments. This calls for a systematic study of classical Y–M theories. A good insight into classical Y–M dynamics would be best obtained by comparing and contrasting the Y–M results with their ED counterparts. In this article, a beginning has been made by considering streaming instabilities in Y–M fluids. We find that in addition to analogues of ED instabilities, novel nonabelian modes arise, reflecting the inherent nonabelian nature of the interaction. The new modes exhibit propagation/ growth, with growth rates that can be larger than what we find in ED. Interestingly, we also find a mode that propagates without getting affected by the medium.

The Two-stream Instability (TSI) generation is studied analytically in the lunar ionosphere. The TSI is a tiny perturbation in the electron plasma density, due to which an electric field grows with time and this growth is facilitated by the electron plasma in the background. In lunar ionosphere, the TSI comes into existence when the solar wind interacts unhindered with the tenuous lunar electron plasma in the surface bound exosphere. In this study, the conditions which allow the TSI to form and the subsequent instability growth with time i.e. the growth factor, is estimated. Initially, the threshold condition for the TSI to take place is determined. Thereafter, the solar wind and lunar plasma parameter contribution to trigger TSI is investigated along with the effect of these parameters in the evolution of TSI. The plasma TSI evolution with the passage of time is also depicted in phase space diagram with Particle-In-Cell simulations. [ABSTRACT FROM AUTHOR]

In this paper the influence of large-scale decreasing and increasing gradients of the density of magnetized plasma on the relaxation process of a continuously injected relativistic electron beam with an energy of 660 keV ( v b = 0.9 c) and a pitch-angle distribution is studied using particle-in-cell numerical simulations. It is found that for the selected parameters in the case of a smoothly decreasing gradient and in a homogeneous plasma the formation of spatially limited plasma oscillations of large amplitude occurs. In such cases, modulation instability develops and a long-wave longitudinal modulation of the ion density is formed. In addition, the large amplitude of plasma waves accelerates plasma electrons to energies on the order of the beam energy. In the case of increasing and sharply decreasing gradients, a significant decrease in the amplitude of plasma oscillations and the formation of a turbulent ion density spectrum are observed. The possibility of acceleration of beam electrons to energies more than 2 times higher than the initial energy of the beam particles is also demonstrated. This process takes place not only during beam propagation in growing plasma density, but also in homogeneous plasma due to interaction of beam particles with plasma oscillations of large amplitude. [ABSTRACT FROM AUTHOR]

This paper develops energy-preserving discontinuous Galerkin (DG) methods for the Vlasov-Ampère (VA) system coupled with the Dougherty-Fokker-Planck (DFP) collision operator. While the classical VA system has been extensively studied, the inclusion of the collision operator introduces new challenges in conserving the total energy of the system. To address this, we design two energy-conserving temporal discretization methods: a second-order explicit scheme and a second-order implicit-explicit (IMEX) scheme. These schemes are coupled with the DG method, specifically using the local DG (LDG) method for the DFP part. We prove that the fully discrete schemes conserve the total particle number and total energy of the VA-DFP system at the fully discrete level. We further establish the L 2 stability of the fully discrete explicit scheme. Numerical experiments are conducted to assess the accuracy, conservation property, and performance of the proposed schemes. [ABSTRACT FROM AUTHOR]

In this work, we investigate the possibility of two-stream instability in the Venusian atmosphere leading to momentum transfer, then to the subsequent escape of hydrogen and oxygen ions from the ionosphere. We employ the hydrodynamic model and obtain the linear dispersion relation from which the two-stream instability is studied. Further, the interaction of solar wind with the ions of Venus ionosphere from which the instability sets in, has been studied using the data from ASPERA-4 of Venus express. The data support the fact that the two-stream instability can provide sufficient energy to accelerate ions to escape velocity of the planet and thus leave the Venusian ionosphere. [ABSTRACT FROM AUTHOR]

In this article, we choose the more complex form of extremely unbalanced initial data, further investigating the performance of the particles and the numerical convergence of the scheme. The proposed algorithm is built up using the philosophy of finite difference and spectral estimates. Time and memory management of the generic code for computational matters are also part of the discussion. The practicality of the presented approach and model, which exploit fractional notions, may tempt the reader to extend to more dimensions. [ABSTRACT FROM AUTHOR]

Subject and Purpose. The research subject is spectral characteristics of the space-charge wave propagating in klystron-type two-stream superheterodyne free-electron laser (TSFEL) with a helical relativistic electron beam. The aim is to theoretically investigate the longitudinal electrostatic field action on the multiharmonic space-charge wave forming in the device under study. Methods and Methodology. We proceed from the quasi-hydrodynamical equation, continuity equation, and Maxwell's equations. Methods of hierarchical approach to the theory of oscillations and waves, namely the modernized method of averaged characteristics, are employed to solve the problems of motion and continuity. The method of slowly varying amplitudes is used to solve the field problem. Results. A differential equation system has been obtained in cubical non-linear approximation, describing the dynamics of multiharmonic space-charge wave harmonics in the TSFEL transit section in the presence of a longitudinal electrostatic field. A regime has been studied where the frequency of the first-order space-charge wave harmonic is much less than the critical frequency of the two-stream instability. It has been demonstrated that the accelerating longitudinal electrostatic field application broadens the frequency spectrum. In the decelerating electrostatic field, the multiharmonic space-charge waves have higher amplitudes and narrower frequency spectra. The transit section length decreases then. It has been revealed that the longitudinal electrostatic field application for controlling the frequency spectrum width is more effective with helical electron beams than with straight ones. Conclusion. We propose to use a longitudinal electrostatic field in the TSFEL transit section for controlling the width of space-charge wave frequency spectrum and the level of output signal amplitudes in multiharmonic two-stream free-electron lasers of klystron type with a helical relativistic electron beam.

Two coupled, interpenetrating fluids suffer instabilities beyond certain critical counterflows. For ideal fluids, an energetic instability occurs at the point where a sound mode inverts its direction due to the counterflow, while dynamical instabilities only occur at larger relative velocities. Here, we discuss two relativistic fluids, one of which is dissipative. Using linearized hydrodynamics, we show that, in this case, the energetic instability turns dynamical, i.e., there is an exponentially growing mode, and this exponential growth only occurs in the presence of dissipation. This result is general and does not rely on an underlying microscopic theory. It can be applied to various two-fluid systems, for instance, in the interior of neutron stars. We also point out that, under certain circumstances, the two-fluid system exhibits a mode analogous to the r-mode in neutron stars that can become unstable for arbitrarily small values of the counterflow.

A class of modular high order forward semi-Lagrangian (FSL) schemes with a number of advantages (outlined below) for linear advection equations is extended to have high resolution, in the sense that sharp gradients can be captured without loss of accuracy, by means of weighted essentially non-oscillatory derivative (DWENO) calculations based on finite differences. Principally, our approach (the convected scheme , CS) differs from conventional high order FSL schemes in the means by which it reaches higher order accuracy. The high order CS progressed in this work reserves use of a low order histogram representation of the solution and a mass-conservative volume-weighted projection operator which ordinarily produces a second order accurate solution. A higher order version is obtained by compensating for the amount by which the CS solution and the exact solution disagree at every order in a Taylor series sense. Instead of including these error terms algebraically, which changes the projection operator itself, the novel idea of the CS is to incorporate this information geometrically as a commensurate adjustment to the volume-weighted proportion assigned to each cell. We leverage DWENO approximations to compute these Taylor series error terms more sensitively, and show the corresponding WENO convected schemes (WENO-CS) achieve the desired dual high order and high resolution behavior. Fifth, seventh, and ninth order WENO-CS base solvers are presented for the 1D constant speed advection equation prototype, and are employed in a Strang splitting approach for the numerical solution of linear and nonlinear two-dimensional hyperbolic equations. Results are showcased for 2D linear transport and rigid body rotation, as well as for classic benchmark problems for the (1 + 1) -dimensional Vlasov–Poisson system including Landau damping, and the two-stream instability. The schemes enjoy the usual benefits of semi-Lagrangian schemes (e.g. no CFL time step restriction) while further claiming distinct advantages afforded to forward schemes including automatic mass conservation, compact support, and therefore straightforward parallelization. [ABSTRACT FROM AUTHOR]

In the cubic non-linear approximation framework, the analysis of space charge wave formation with a wide frequency spectrum in helical two-velocity electron beams was performed. It was shown that the formation of a space charge wave with wide frequency spectrum in this kind of beams occurs on condition that the wave first harmonic frequency is much less than the two-stream instability critical frequency. We demonstrated that due to the linearity of the growing space charge wave dispersion characteristic, the condition of the three-wave parametric resonant interactions in helical two-stream relativistic electron beam fulfills for a significant number of such wave’s harmonics which frequencies are less than the critical frequency. Due to these resonances, the excitation of multiharmonic space charge wave occurs. This wave is amplified due to both the three-wave parametric resonances and the two-stream instability mechanism. As a result, the multiharmonic space charge wave forms, and its spectrum width is defined by the 1st harmonic frequency and the two-stream instability critical frequency. It is demonstrated that the frequency spectrum width of the multiharmonic space charge wave increases with the increase of the electrons input angle with respect to the longitudinal focusing magnetic field and it exceeds the frequency spectrum width of such waves in straight electron beams. It is also found out that the space charge wave saturation length in a helical electron beam is two and more times less than in straight electron beams. Therefore, the devices using two-stream helical relativistic electron beams would have less longitudinal dimensions. We proposed to use helical two-stream relativistic electron beams in multiharmonic two-stream superheterodyne freeelectron lasers in order to increase the frequency spectrum width and to decrease the device’s longitudinal dimensions compared with devices using straight electron beams. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the effect of the filter for the hyperbolic moment equations (HME) (Cai et al. in Commun Pure Appl Math 67(3):464–518, 2014; Cai et al. in SIAM J Sci Comput 35(6):A2807–A2831, 2013) of the Vlasov–Poisson equations and propose a novel quasi time-consistent filter to suppress the numerical recurrence effect. By taking properties of HME into consideration, the filter preserves a lot of physical properties of HME, including Galilean invariance and conservation of mass, momentum and energy. We present two viewpoints—collisional viewpoint and dissipative viewpoint—to dissect the filter, and show that the filtered hyperbolic moment method can be treated as a solver of the Vlasov equation. Numerical simulations of the linear Landau damping and two stream instability demonstrate the effectiveness of the filter in restraining recurrence arising from particle streaming. Both the analysis and the numerical results indicate that the filtered method can capture the evolution of the Vlasov equation, even when phase mixing and filamentation dominate. [ABSTRACT FROM AUTHOR]

We have developed a 2.5-dimensional electromagnetic particle simulation code using the particle-in-cell (PIC) method to investigate electromagnetic phenomena that occur in space plasmas. Our code is based on the leap-frog method and the centered difference method for integration and differentiation of the governing equations. We adopted the relativistic Buneman-Boris method to solve the Lorentz force equation and the Esirkepov method to calculate the current density while maintaining charge conservation. Using the developed code, we performed test simulations for electron two-stream instability and electron temperature anisotropy induced instability with the same initial parameters as used in previously reported studies. The test simulation results are almost identical with those of the previous papers.

We elaborated a self-consistent cubic-nonlinear theory of multiharmonic two-stream superheterodyne free-electron lasers (TSFELs) of klystron type with helical relativistic electron beams (REBs). We investigated the operation mode, in which the first harmonic of electromagnetic signal is much less than the twostream instability critical frequency. We accounted plural three-wave resonant interactions of different wave types. It was demonstrated that application of helical beams in TSFEL klystrons allows achieving a powerful multiharmonic electromagnetic signal with wider frequency spectrum compared with TSFEL based on straight beams. We showed that growth rates of electromagnetic waves in TSFELs with helical beams are substantially higher and the saturation lengths are much shorter. It allows decreasing longitudinal dimensions of TSFELs. We illustrated the application perspective of the klystron type TSFELs with helical REBs in the field of powerful multiharmonic electromagnetic waves with wide frequency spectrum forming. [ABSTRACT FROM AUTHOR]

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The electron-electron two-stream instability has been studied in two-valley n-GaAs embedded with nanoparticle (NP) cluster. We considered polar optical phonon as the dominant intravalley scattering mechanism and drifted Maxwellian to approximate the distribution of carriers between each valley. We derived the dispersion relation for electrostatic wave using hydrodynamic model of plasmas. While investigating temporal behaviour, we found two novel modes of propagation. These two novel modes are found to be evanescent by nature and propagate with equal phase velocities, but in opposite directions. The pre-existing modes retained their profile structures even in the presence of NP cluster. On the other hand, in the case of convective instability, no new modes are obtained but the propagation and gain profiles of the preexisting modes are significantly modified by the presence of NP cluster in the host medium. [ABSTRACT FROM AUTHOR]