Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Plasma kinetic simulation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Particle Acceleration by Dense Impulsive Structures Moving in Ambient Magnetospheric Plasma. 3-D Hybrid Kinetic Modeling and MMS Observations

High resolution observations of dense plasma impulsive structures moving through an ambient background magnetospheric flows were captured by the Magnetospheric Multiscale mission. The observations show particle heating and acceleration, shock-like wave formation, and whistler wave excitation inside the interface between the dense impulsive plasma structures and the ambient plasma. A multiscale hybrid kinetic simulation provides an explanation of the observed wave-particle interactions with the assumption that the dense plasma structures may be represented by plasma clouds which are formed at the magnetopause layer due to reconnection processes. Plain Language Summary: Dense, impulsive plasma structures moving through a background plasma were captured by the NASA Magnetospheric Multiscale mission. The observations show that the dense structures can generate strong perturbations in the electromagnetic field and shock-like waves. Interactions between these electromagnetic waves and the particles results in particle acceleration. 3-D hybrid kinetic modeling (particle description for ions and fluid description for electrons) was used to investigate the plasma physics of the observed structures. It was assumed that the plasma clouds were formed by magnetic field reconnection inside the magnetopause, which is the interface between the solar wind particles and the cold low-density magnetospheric plasma. The work helps us understand the plasma environment at the interface between the Earth and solar wind, near planetary moons, within astrophysical explosions, and possibly at the interface between the solar wind and local interstellar medium.

A. S. Lipatov↗
NASA NTRS2012

Multi-Scale Modeling of Magnetospheric Dynamics

Magnetic reconnection is a key element in many phenomena in space plasma, e.g. Coronal mass Ejections, Magnetosphere substorms. One of the major challenges in modeling the dynamics of large-scale systems involving magnetic reconnection is to quantifY the interaction between global evolution of the magnetosphere and microphysical kinetic processes in diffusion regions near reconnection sites. Recent advances in small-scale kinetic modeling of magnetic reconnection significantly improved our understanding of physical mechanisms controlling the dissipation in the vicinity of the reconnection site in collisionless plasma. However the progress in studies of small-scale geometries was not very helpful for large scale simulations. Global magnetosphere simulations usually include non-ideal processes in terms of numerical dissipation and/or ad hoc anomalous resistivity. Comparative studies of magnetic reconnection in small scale geometries demonstrated that MHD simulations that included non-ideal processes in terms of a resistive term 11 J did not produce fast reconnection rates observed in kinetic simulations. In collisionless magnetospheric plasma, the primary mechanism controlling the dissipation in the vicinity of the reconnection site is nongyrotropic pressure effects with spatial scales comparable with the particle Larmor radius. We utilize the global MHD code BATSRUS and replace ad hoc parameters such as "critical current density" and "anomalous resistivity" with a physically motivated model of dissipation. The primary mechanism controlling the dissipation in the vicinity of the reconnection site in incorporated into MHD description in terms of non-gyrotropic corrections to the induction equation. We will demonstrate that kinetic nongyrotropic effects can significantly alter the global magnetosphere evolution. Our approach allowed for the first time to model loading/unloading cycle in response to steady southward IMF driving. The role of solar wind parameters and ionospheric conductance on the dynamics of the loading/unloading cycle will be discussed.

Kuznetsova, M. M.↗
NASA NTRS2013

Jovian Plasmas Torus Interaction with Europa. Plasma Wake Structure and Effect of Inductive Magnetic Field: 3D Hybrid Kinetic Simulation

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to a variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo Orbiter mission, and for planning flyby and orbital measurements (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy et al., 2007; Shematovich et al., 2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyroradius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream background ions). Photoionization, electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider the models with Oþ þ and Sþ þ background plasma, and various betas for background ions and electrons, and pickup electrons. The majority of O2 atmosphere is thermal with an extended non-thermal population (Cassidy et al., 2007). In this paper, we discuss two tasks: (1) the plasma wake structure dependence on the parameters of the upstream plasma and Europa's atmosphere (model I, cases (a) and (b) with a homogeneous Jovian magnetosphere field, an inductive magnetic dipole and high oceanic shell conductivity); and (2) estimation of the possible effect of an induced magnetic field arising from oceanic shell conductivity. This effect was estimated based on the difference between the observed and modeled magnetic fields (model II, case (c) with an inhomogeneous Jovian magnetosphere field, an inductive magnetic dipole and low oceanic shell conductivity).

Jovian magnetosphere↗
NASA NTRS1987

A possible explanation of the electron temperature enhancement in the wake of a satellite

A numerical simulation was performed in an attempt to explain the enhancement of electron temperature in the wake of an ionospheric satellite in terms of counterstreaming plasma expansions. The simulation was conducted using full kinetic treatments (Vlasov-Poisson code) for both the plasma electrons and ions. The calculations indicated that at a distance of a few Debye lengths from the surface of the body the wake/ambient electron-temperature ratio reaches a value of about 2. This result is in good agreement with some in situ and laboratory experimental results.

Singh, Nagendra↗
NASA NTRS2011

Solar Wind Access to Lunar Polar Craters: Feedback Between Surface Charging and Plasma Expansion

Determining the plasma environment within permanently shadowed lunar craters is critical to understanding local processes such as surface charging, electrostatic dust transport, volatile sequestration, and space weathering. In order to investigate the nature of this plasma environment, the first two-dimensional kinetic simulations of solar wind expansion into a lunar crater with a self-consistent plasma-surface interaction have been undertaken. The present results reveal how the plasma expansion into a crater couples with the electrically-charged lunar surface to produce a quasi-steady wake structure. In particular, there is a negative feedback between surface charging and ambipolar wake potential that allows an equilibrium to be achieved, with secondary electron emission strongly moderating the process. A range of secondary electron yields is explored, and two distinct limits are highlighted in which either surface charging or ambipoiar expansion is responsible for determining the overall wake structure.

Zimmerman, M. I.↗
NASA NTRS1987

Core plasma in the magnetosphere

The paper presents a review of new findings related to core plasma (which includes ions and electrons with energies less than 50 eV) identified in studies of magnetosphere during 1983-1986. These findings include the cleft ion fountain; the plasmaspheric heavy ion torus; core molecular ions; high core-plasma densities in the plasma-sheet boundary layer; intense transverse heating of core plasmas in the equatorial regions; the supersonic polar wind (H/+/ and He/+/); toroidal or ring heavy-ion distribution functions in the auroral region; conic-to-field-aligned ion signatures of inverted-V auroral events; and the large-scale electron density structure of the magnetosphere. The progress made on modeling core plasma includes simulation of thermal helium heating at the equator; kinetic models of the plasma transport from localized ionospheric regions; time-dependent hydrodynamic models of the polar wind and plasmasphere-ionosphere coupling; and kinetic models of plasmasphere refilling.

Horwitz, J. L.↗
NASA NTRS1990

Linear and non-linear studies of Alfven waves in space. Stationary and dynamic processes in magnetospheric plasmas

The Final Technical Report on linear and non-linear studies of Alfven waves in space is presented. Areas of research included relaxation of magnetotail plasmas with field-aligned currents; the equilibrium dayside magnetosphere; macroscale particle simulation of kinetic Alfven wave physics; ballooning stability of plasmas with sheared equilibrium flows; theory of the drift-mirror instability; collisionless tearing instability in magnetotail plasmas; and nonadiabatic behavior of the magnetic moment of a charged particle in a dipole magnetic field and the development of stochastic webs.

Bhattacharjee, A.↗
NASA NTRSDate not supplied

Simulation of Vacuum Chamber Pressure Distribution with Surrogate Modeling and Uncertainty Quantification

A major challenge in understanding differences in electric propulsion performance in ground tests and in space operations concerns the pressure distribution within the test vacuum chamber. The chamber backpressure is much higher than experienced in space, modifying thruster performance and plume dynamics. Numerical simulation is a key element to determining the background conditions in non-ideal vacuum chamber environments. An important parameter for the accurate simulation of chamber backpressure is the probability that an atom will stick to a cryogenic panel used to pump away the plume gases. This quantity can be used to model vacuum pumps in particle-based kinetic numerical methods. In this work, a three-dimensional direct simulation Monte Carlo code is used to model neutral xenon atoms flowing from the anode of the H9 Hall Effect Thruster within the University of Michigan’s Large Vacuum Test Facility. Simulated pressures are compared with ion gauge pressure measurements to infer the effective sticking coefficient of the chamber’s vacuum pumps. A pressure predicting surrogate model is developed for inference of pump sticking coefficients and for uncertainty quantification. This information enables accurate and useful kinetic simulations of electric propulsion thruster plasma plumes in vacuum chambers.

DSMC↗
NASA NTRS2012

Ringing After a High-Energy Collision: Ambipolar Oscillations During Impact Plasma Expansion

High-velocity impacts on the Moon and other airless bodies deliver energy and material to the lunar surface and exosphere. The target and i mpactor material may become vaporized and ionized to form a collision al plasma that expands outward and eventually becomes collisionless. In the present work, kinetic simulations of the later collision less stage of impact plasma expansion are performed. Attention is paid to characterizing "ambipolar oscillations" in which thermodynamic distur bances propagate outward to generate "ringing" within the expanding e lectron cloud, which could radiate an electromagnetic signature of lo cal plasma conditions. The process is not unlike a beam-plasma intera ction, with the perturbing electron population in the present case ac ting as a highly thermal "beam" that resonates along the expanding de nsity gradient. Understanding the electromagnetic aspects of impact p lasma expansion could provide insight into the lasting effects of nat ural, impact-generated currents on airless surfaces and charging haza rds to human exploration infrastructure and instrumentation.

Zimmerman, M. I.↗
NASA NTRS2014

Concerning the Charging of an Exploration Craft on and near a Small Asteroid

Introduction: An object immersed in an airless plasma environment will experience a natural process of surface charging in order to acheieve current balance, or zero net electric current to the object. It has been shown in recent computer simulations that the small-body plasma environment is very complex [1], considering effects of photoemission, topography, and formation of a plasma wake. For this work we consider an exploration craft (or astronaut) immersed within a plasma environment near an asteroid, which exhibits widely varying solar wind and photoelectric particle fluxes and continuously evolving illumination conditions. Objective: We aim to determine how an explo-ration craft or astronaut suit accumulates charge while located in the "nightside" asteroid wake where the particle fluxes are reduced, and in the dayside near-surface photoelectron sheath, by combining an object charging model [2] with kinetic simulations of a near-asteroid plasma environment [1]. We consider an astronaut floating near the asteroid while not in contact with the surface, as well as an astronaut moving along the surface using their hands/gloves to crawl along. Results: The modeling results suggest that remediation of triboelectric charge via accumulation of plasma currents is an important factor to consider when designing future NEA mission infrastructure, especially if repeated and frequent contact with the surface is planned. In shadowed regions such as the location shown in Fig. 1a, the plasma currents are so low (and the effective charge-remediation timescale so long, e.g. minutes to hours) that repeated contact with the surface tribocharges the glove in an uncontrollable fashion, as shown for two representative electron temperatures in Fig. 2a. The resulting buildup of significant negative charge would eventually initiate some other "current of last resort" [4] such as transport of positively-charged dust, field-emission from the glove, or significant alteration of environmental ion currents within the wake. In contrast, the few-meters-thick dayside photoelectron sheath in which the astronaut of Fig. 1b is immersed in is so rich in electrons (and hence so electrically conductive) that accumulated tribocharge dissipates almost instantaneously (e.g. in less than a ms) as shown in Fig. 2b. As our model astronaut orbits the NEA they would experience plasma currents and associated charge re-mediation times spanning many orders of magnitude, and the fusion between our numerical models provides a detailed understanding of the charging hazards possibly associated with contact-based NEA exploration.

Asteroid↗
NASA NTRS1995

Theoretical Plasma Distribution Consistent With Ulysses Magnetic Field Observations in a High-Speed Solar Wind Tangential Discontinuity

The overall multi-layer structure of the magnetic field observed by Ulysses across a broad solar wind tangential discontinuity can be reproduced fairly well by means of a kinetic model. Such a simulation provides complementary information about the velocity distribution functions, which are not always known due to the low time resolution inherent in plasma measurements. The success of such a simulation proves that our kinetic model can be used as a realistic basis for further studies of the structure and stability of tangential discontinuities.

solar wind Ulysses plasma↗
NASA NTRS1987

The interaction of quasiperpendicular shock waves in a collisionless plasma

The interaction between collisionless shocks is examined from a kinetic viewpoint using computer simulations of shock collisions spanning the range of ambient plasma and shock parameters typical of the interplanetary medium. It is found that the interaction between two subcritical, perpendicular shocks is largely fluidlike with no evidence for accelerated particles. The electromagnetic fields associated with each shock, but not the plasmas, pass through each other during the collision. This interaction is due to self-consistently generated electric fields which adjust to the value needed to bring to rest the two incoming streams. The interaction between two supercritical perpendicular collisionless shocks is similar to the subcritical case, in that the electromagnetic fields associated with each shock are transmitted whereas particles are not. However, the interaction is also highly dynamic with substantial acceleration of ions. Increasing the Mach number gives rise to an increasing number of energetic particles.

Cargill, P. J.↗
NASA NTRS2008

Plasma Sheet Circulation Pathways

Global simulations of Earth's magnetosphere in the solar wind compute the pathways of plasma circulation through the plasma sheet. We address the pathways that supply and drain the plasma sheet, by coupling single fluid simulations with Global Ion Kinetic simulations of the outer magnetosphere and the Comprehensive Ring Current Model of the inner magnetosphere, including plasmaspheric plasmas. We find that the plasma sheet is supplied with solar wind plasmas via the magnetospheric flanks, and that this supply is most effective for northward IMF. For southward IMF, the innermost plasma sheet and ring current region are directly supplied from the flanks, with an asymmetry of single particle entry favoring the dawn flank. The central plasma sheet (near midnight) is supplied, as expected, from the lobes and polar cusps, but the near-Earth supply consists mainly of slowly moving ionospheric outflows for typical conditions. Work with the recently developed multi-fluid LFM simulation shows transport via plasma "fingers" extending Earthward from the flanks, suggestive of an interchange instability. We investigate this with solar wind ion trajectories, seeking to understand the fingering mechanisms and effects on transport rates.

Moore, Thomas E.↗
NASA NTRS1992

Hybrid simulations of intermediate shocks - Coplanar and noncoplanar solutions

A hybrid code is used to investigate the kinetic structure and stability of subfast intermediate shocks (IS) formed dynamically by the interaction between a flowing plasma and a stationary piston. Results of the kinetic simulation of noncoplanar ISs are compared with predictions of the MHD theory. The relevance of the results of the study to observations of the magnetopause is discussed.

Karimabadi, H.↗
NASA NTRS2023

Oblique Propagation and Temperature Effects on the Resonant Right-Hand Ion Beam Instability

The resonant right-hand instability (RHI) is often the dominant mode driven by reflected ions upstream of Earth’s quasi-parallel bow shock. In the tradition of Peter Gary, this paper further explores the right-hand instability using numerical solutions of the plasma dispersion relation and non-linear kinetic simulations, with parameters inspired by observations from NASA’s Magnetospheric Multiscale (MMS) mission. Agreement is found between the ion distributions in the particle-in-cell simulations and Magnetospheric Multiscale spacecraft data, which show the gyrophase bunching characteristic of the instability. The non-linear structures created by right-hand instability tend to be stronger when the plasma beta is lower. These structures have sizes of around 100 to 200 ion inertial lengths perpendicular to the magnetic field, presenting planet-sized disturbances to the magnetosphere. 2d and 3D hybrid particle-in-cell simulations show that modes with a range of propagation angles oblique to the magnetic field are excited, providing a ground to understand previous statistical studies of observed foreshock waves.

Ari Le↗