If the electron distribution function is approximately bi‐Maxwellian with T ⊥ / ‖ > 1, where subscript symbols denote directions perpendicular and parallel to background magnetic field, if this temperature anisotropy sufficiently large, whistler instability excited. This mode studied using two‐dimensional particle‐in‐cell simulations in a spatially homogeneous plasma model. Theory predicts threshold for which depends inversely on β. The show that wave‐particle scattering by enhanced...

Social studies researchers use graphs to model group activities in social networks. An important property this context is the centrality of a vertex: inverse average distance each other vertex. We describe randomized approximation algorithm for weighted graphs. For exhibiting small world phenomenon, our method estimates all vertices with high probability within (1+epsilon) factor near-linear time.

Abstract Large constellations of small satellites will significantly increase the number objects orbiting Earth. Satellites burn up at end service life during reentry, generating aluminum oxides as main byproduct. These are known catalysts for chlorine activation that depletes ozone in stratosphere. We present first atomic‐scale molecular dynamics simulation study to resolve oxidation process satellite's structure mesospheric and investigate depletion potential from oxides. find demise a...

The electromagnetic proton cyclotron instability and the mirror are driven by temperature anisotropy T ⊥ p / ‖ > 1, where denote directions relative to background magnetic field. Linear theory one‐dimensional hybrid simulations imply that former mode grows more rapidly over 0.05 ≤ β 5 wave‐particle scattering its enhanced fluctuations imposes an upper bound on of form urn:x-wiley:01480227:media:jgra13669:jgra13669-math-0001 B 0 is Here S α fitting parameters, . This paper describes...

It is shown that the dominant nonlinear effect makes evolution of whistler turbulence essentially three dimensional in character. Induced scattering due to slow density perturbation resulting from ponderomotive force triggers energy flux toward lower frequency. Anisotropic wave vector spectrum generated by large angle scatterings thermal plasma particles, which propagation substantially altered but frequency changes a little. As consequence, does not indicate trajectory flux. There can be...

This manuscript describes the first ensemble of three-dimensional (3D) particle-in-cell (PIC) plasma simulations whistler turbulence. The computational model represents a collisionless, homogeneous, magnetized on which an initial spectrum relatively long wavelength fluctuations is imposed. represent range fluctuation amplitudes and follow temporal evolution system as it decays into broadband, anisotropic, turbulent at shorter wavelengths via forward cascade. resulting 3D turbulence similar...

A fully three-dimensional computer particle simulation model for ion optics is developed. This allows multiple apertures to be included explicitly in the domain and determines upstream sheath downstream beam neutralization through simulations. Simulations are performed NSTAR ion-thruster optics, results compared with grid-erosion measurements obtained during long-duration test. It shown that not only predicts accurately all of features measured erosion pattern but also gives excellent...

This paper presents a fully kinetic particle-in-cell simulation of collisionless mesothermal plasma expansion with focus on the macroscopic electron properties. The results show that thermal properties are anisotropic and nonuniform. In beam core region, electrons thermalized due to interactions between trapped potential well exit front. inside is equilibrium significant cooling occurs associated expansion. Immediately out boundary, undergo an isothermal outer transition into nonequilibrium...

Three‐dimensional particle‐in‐cell (PIC) simulations of whistler turbulence at three different initial values β e are carried out on a collisionless, homogeneous, magnetized plasma model. The begin with an ensemble relatively long‐wavelength modes and follow the temporal evolution fluctuations as wave‐wave interactions lead to forward cascade into broadband, turbulent spectrum shorter wavelengths wave vector anisotropy in sense k ⟂ > ∥ . Here denote directions perpendicular parallel...

Full particle particle-in-cell simulations are performed to study the collisionless electron-ion coupling during ion beam emission and neutralization. Simulations show that neutralization propagation two closely coupled processes. Electron-ion is achieved through interactions between trapped electrons a potential well established by of front along direction not plasma instabilities as previous studies suggested. In transverse direction, generates an expansion fan similar mesothermal into...

We present a particle-in-cell (PIC) method using nonhomogeneous immersed-finite-element (IFE) field solver for modeling dielectric surface charging of complex-shaped objects in plasmas. The IFE allows PIC codes Cartesian mesh applied to simulations involving arbitrarily shaped with similar accuracy as that body-fitting mesh. object is treated an interface. Surface calculated directly from charge deposition at the interface, and electrostatic fields on both sides interface are resolved...

ABSTRACT The decay of whistler turbulence in a collisionless, homogeneous, magnetized plasma is studied using three-dimensional particle-in-cell simulations. simulations are initialized with narrowband, relatively isotropic distribution long wavelength modes. A first ensemble at electron beta <?CDATA ${\beta }_{{\rm{e}}}$?> <?MML <mml:math> <mml:msub> <mml:mrow> <mml:mi>&beta;</mml:mi> </mml:mrow> <mml:mi mathvariant="normal">e</mml:mi> </mml:msub> </mml:math>?> = 0.25 and ion-to-electron...

Detailed quantum-chemistry calculations of field-induced fragmentation reactions ionic liquid are presented. The simulations identified the most likely channels for hard (breaking covalent bonds) fragmentation. computed energetics and soft clusters into moieties) can be incorporated in multiscale models thrusters’ operation. determined that occurs on a picosecond scale, revealing these large flexible ions heated when accelerated by electric field. Although acquired internal kinetic energy...

[1] The first fully three-dimensional particle-in-cell (PIC) simulation of whistler turbulence in a magnetized, homogeneous, collisionless plasma has been carried out. An initial relatively isotropic spectrum long-wavelength whistlers is imposed upon the system, with an electron β = 0.10. As previous two-dimensional simulations turbulence, system exhibits forward cascade to shorter wavelengths and broadband, turbulent spectra wave vector anisotropy sense stronger fluctuation energy at k⊥...

This paper presents a fully kinetic particle particle-in-cell simulation study on the emission of collisionless plasma plume consisting cold beam ions and thermal electrons. Results are presented for both two-dimensional macroscopic structure microscopic electron characteristics. We find that exhibits several distinctive regions, including an undisturbed core region, cooling expansion isothermal region. The properties each region determined by division between approximately matches Mach line...

Abstract Three-dimensional particle-in-cell simulations of the forward cascade decaying kinetic Alfvén turbulence have been carried out as an initial-value problem on a collisionless, homogeneous, magnetized, electron–ion plasma model with and m i / e = 100, where subscripts represent electrons ions, respectively. Initial anisotropic narrowband spectra relatively long-wavelength modes approximately gyrotropic distributions in undergo to broadband magnetic fluctuations at shorter wavelengths....

Both fully kinetic and hybrid particle-in-cell (PIC) simulations are performed to investigate the two-dimensional (2D) expansion of a collisionless, hypersonic plasma plume into vacuum. The PIC carried out using real ion-to-electron mass ratios H^{+}, Ar^{+}, Xe^{+}, while model assumes electrons be massless, isothermal fluid. We find that exhibits four distinct regions, unperturbed, quasisteady expansion, self-similar electron front regions. behavior is strongly anisotropic, causing...

The physics of ionic electrospray propulsion spans multiple length scales. This paper combines a molecular dynamics model, particle–particle and particle-in-cell model to investigate the over 9 orders magnitude in scale. combined models are applied simulate beam emission for an system with porous emitter tips 1-ethyl-3-methylimidazolium tetrafluoroborate liquid propellant from site downstream plume. Additionally, impact sites single tip is analyzed regard extractor grid interception overall...

This paper presents experimental research to determine the charge of individual dust grains on a lunar regolith simulant surface immersed in plasma. The results show that, at similar charging potentials, both and charge-to-mass ratio JSC-1A is about two orders magnitude smaller than that single, isolated particle.

Direct simulation Monte Carlo and particle-in-cell simulations are carried out to study the potential of a mesothermal plasma plume in vacuum chamber. The results show that beam with respect ambient chamber is different from space because facility can prematurely terminate expansion process. As result, measured may be significantly lower than under in-space condition. This lead underestimation backflow charge-exchange ions ionized contaminants thruster modeling.

Abstract Three‐dimensional particle‐in‐cell simulations of decaying whistler turbulence are carried out on a collisionless, homogeneous, magnetized, electron‐ion plasma model. The use an initial ensemble relatively long wavelength modes with broad range propagation directions electron beta β e = 0.05. computations follow the temporal evolution fluctuations as they cascade into broadband turbulent spectra at shorter wavelengths. Three correspond to successively larger simulation boxes and...

We present a new Retarding Potential Analyzer (RPA) design that is capable of measuring keV-level energy, high-density plasma beams. This instrument overcomes the limitations existing RPAs and can operate in plasmas with densities excess 1 × 1015 m-3 ion energies up to 1200 eV. The RPA parameters were determined by analyzing electron density temperature, sheath thickness, beam based on Faraday probe Langmuir measurements. A previously unobserved grid spacing arcing phenomenon was observed...