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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.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Magnetic Field Effects on Plasma Plumes

Here, we will discuss our numerical studies of plasma jets and loops, of basic interest for plasma propulsion and plasma astrophysics. Space plasma propulsion systems require strong guiding magnetic fields known as magnetic nozzles to control plasma flow and produce thrust. Propulsion methods currently being developed that require magnetic nozzles include the VAriable Specific Impulse Magnetoplasma Rocket (VASIMR) [1] and magnetoplasmadynamic thrusters. Magnetic nozzles are functionally similar to de Laval nozzles, but are inherently more complex due to electromagnetic field interactions. The two crucial physical phenomenon are thrust production and plasma detachment. Thrust production encompasses the energy conversion within the nozzle and momentum transfer to a spacecraft. Plasma detachment through magnetic reconnection addresses the problem of the fluid separating efficiently from the magnetic field lines to produce maximum thrust. Plasma jets similar to those of VASIMR will be studied with particular interest in dual jet configurations, which begin as a plasma loops between two nozzles. This research strives to fulfill a need for computational study of these systems and should culminate with a greater understanding of the crucial physics of magnetic nozzles with dual jet plasma thrusters, as well as astrophysics problems such as magnetic reconnection and dynamics of coronal loops.[2] To study this problem a novel, hybrid kinetic theory and single fluid magnetohydrodynamic (MHD) solver known as the Magneto-Gas Kinetic Method is used.[3] The solver is comprised of a "hydrodynamic" portion based on the Gas Kinetic Method and a "magnetic" portion that accounts for the electromagnetic behaviour of the fluid through source terms based on the resistive MHD equations. This method is being further developed to include additional physics such as the Hall effect. Here, we will discuss the current level of code development, as well as numerical simulation results

Ebersohn, F.↗
NASA NTRS1986

Physics through the 1990s: Plasmas and fluids

The volume contains recommendations for programs in, and government support of, plasma and fluid physics. Four broad areas are covered: the physics of fluids, general plasma physics, fusion, and space and astrophysical plasmas. In the first section, the accomplishments of fluid physics and a detailed review of its sub-fields, such as combustion, non-Newtonian fluids, turbulence, aerodynamics, and geophysical fluid dynamics, are described. The general plasma physics section deals with the wide scope of the theoretical concepts involved in plasma research, and with the machines; intense beam systems, collective and laser-driven accelerators, and the associated diagnostics. The section on the fusion plasma research program examines confinement and heating systems, such as Tokamaks, magnetic mirrors, and inertial-confinement systems, and several others. Finally, theory and experiment in space and astrophysical plasma research is detailed, ranging from the laboratory to the solar system and beyond. A glossary is included.

Source record↗
NASA NTRS1991

Research briefing on contemporary problems in plasma science

An overview is presented of the broad perspective of all plasma science. Detailed discussions are given of scientific opportunities in various subdisciplines of plasma science. The first subdiscipline to be discussed is the area where the contemporary applications of plasma science are the most widespread, low temperature plasma science. Opportunities for new research and technology development that have emerged as byproducts of research in magnetic and inertial fusion are then highlighted. Then follows a discussion of new opportunities in ultrafast plasma science opened up by recent developments in laser and particle beam technology. Next, research that uses smaller scale facilities is discussed, first discussing non-neutral plasmas, and then the area of basic plasma experiments. Discussions of analytic theory and computational plasma physics and of space and astrophysical plasma physics are then presented.

Source record↗
NASA NTRS2008

The Dissipation Mechanism of Magnetic Reconnection

Magnetic reconnection is arguably the most efficient transport and energy conversion mechanism in almost ideal plasmas. Reconnection controls the overall dynamics in space and astrophysics plasmas, as well as in many laboratory plasma systems. Reconnection operates by means of a localized diffusion region, where deviations from the plasma idealness condition generate electric fields and permit plasma transport even far away from the diffusion region itself. Recent advances in analytic theory and computer modeling have begun to shed light on the internal dynamics of the diffusion region. In particular, we begin to understand the delicate nature of the force balance in the inner diffusion region, where particles can become unmagnetized and where electric field forces are important. This presentation will provide a brief introduction of the reconnection process and its applications. This introduction will be followed by a detailed analysis of the current understanding of dissipation region physics, and by an outlook toward future research.

Hesse, Michael↗
NASA NTRS2008

The Dissipation Mechanism of Magnetic Reconnection

Magnetic reconnection is arguably the most efficient transport and energy conversion mechanism in almost ideal plasmas. Reconnection controls the overall dynamics in space and astrophysics plasmas, as well as in many laboratory plasma systems. Reconnection operates by means of a localized diffusion region, where deviations from the plasma idealness condition generate electric fields and permit plasma transport even far away from the diffusion region itself. Recent advances in analytic theory and computer modeling have begun to shed light on the internal dynamics of the diffusion region. In particular, we begin to understand the delicate nature of the force balance in the inner diffusion region, where particles can become unmagnetized and where electric field forces are important. This presentation will provide a brief introduction of the reconnection process and its applications. This introduction will be followed by a detailed analysis of the current understanding of dissipation region physics, and by an outlook toward future research.

Hesse, Michael↗
NASA NTRS2007

The Inner Workings of Magnetic Reconnection

Magnetic reconnection is arguably the most efficient transport and energy conversion mechanism in almost ideal plasmas. Reconnection controls the overall dynamics in space and astrophysics plasmas, as well as in many laboratory plasma systems. Reconnection operates by means of a localized diffusion region, where deviations from the plasma idealness condition generate electric fields and permit plasma transport even far away from the diffusion region itself. Recent advances in analytic theory and computer modeling have begun to shed light on the internal dynamics of the diffusion region. In particular, we begin to understand the delicate nature of the force balance in the inner diffusion region, where particles can become unmagnetized and where electric field forces are important. This presentation will provide a brief introduction of the reconnection process and its applications. This introduction will be followed by a detailed analysis of the current understanding of dissipation region physics, and by an outlook toward future research.

Hesse, Michael↗
NASA NTRSDate not supplied

The Foundations of Modern Magnetic Reconnection Research

Magnetic reconnection is a fundamental process operating in laboratory, space, and astrophysical plasmas. We understand today that it is the mechanism behind the often explosive release of the stored magnetic energy, and that it directly or indirectly powers as diverse a set of phenomena as solar eruptions, stellar flares, geomagnetic storms, the aurora, and even disruption events in fusion machines. It is also the mechanism powering the majority of the deleterious space effects collectively referred to as “space weather.” Owing to its importance, reconnection has been a research focus for many years, culminating in the research based on NASA’s Magnetospheric Multiscale mission. A major component of foundational research involved studies of the stability and disruption of current sheets by collisionless tearing, which still plays a major role in the dynamical evolution of the interfaces between magnetic fields of different directions. This presentation will illuminate these beginnings, with special focus on the seminal work of Academician A. A. Galeev, and also provide a summary of the present state of knowledge. It will conclude with an outlook toward future reconnection research targets.

Plasma↗
NASA NTRS2004

Seeing the Invisible with the IMAGE Mission

The Global Positioning System, communication, power transmission, and oil pipelines are only a few of the technologies upon which we depend in research and in everyday life. Each is at risk from invisible storms in near-Earth space. The astrophysical plasmas near our planet store and deliver vast amounts of energy from the Sun in the form of high energy particles, electric currents, and heating of the upper atmosphere. This natural plasma environment is the only one routinely measured in situ over the last 40 years and until recently one of the few we haven't been able to see. Much like atmospheric weather satellites brought global context to that field many decades ago, the IMAGE Mission is now revealing a global context for space weather. The contributions being made by the IMAGE Mission to understanding space weather will be presented along with a brief overview of this dynamic environment. Special emphasis will be placed on research involving the plasmasphere, a toroidal region of relatively dense, cold plasma surrounding the Earth that plays a key role in energy and mass transport through near-Earth space.

Gallagher, D. L.↗
NASA NTRS1992

Does fast magnetic reconnection exist?

The main features of the Priest-Forbes (1986) and Priest-Lee (1990) models of magnetic reconnection in astrophysical plasmas are discussed, and the Priest-Lee model is generalized to include inflow pressure gradients and thus different regimes of reconnection. It is shown that different scaling results can be obtained depending on the boundary conditions. These results are compared to the ones observed in the numerical experiments of Biskamp (1986) and Lee and Fu (1986). It is concluded that numerical experiments with suitably designed boundary conditions are likely to exhibit fast reconnection, and that such reconnection is a common process in astrophysical and space plasmas.

Priest, E. R.↗
NASA NTRS2009

Combined Modeling of Acceleration, Transport, and Hydrodynamic Response in Solar Flares: The Numerical Model - 1

Acceleration and transport of high-energy particles and fluid dynamics of atmospheric plasma are interrelated aspects of solar flares, but for convenience and simplicity they were artificially separated in the past. We present here self consistently combined Fokker-Planck modeling of particles and hydrodynamic simulation of flare plasma. Energetic electrons are modeled with the Stanford unified code of acceleration, transport, and radiation, while plasma is modeled with the Naval Research Laboratory flux tube code. We calculated the collisional heating rate directly from the particle transport code, which is more accurate than those in previous studies based on approximate analytical solutions. We repeated the simulation of Mariska et al. with an injection of power law, downward-beamed electrons using the new heating rate. For this case, a -10% difference was found from their old result. We also used a more realistic spectrum of injected electrons provided by the stochastic acceleration model, which has a smooth transition from a quasi-thermal background at low energies to a non thermal tail at high energies. The inclusion of low-energy electrons results in relatively more heating in the corona (versus chromosphere) and thus a larger downward heat conduction flux. The interplay of electron heating, conduction, and radiative loss leads to stronger chromospheric evaporation than obtained in previous studies, which had a deficit in low-energy electrons due to an arbitrarily assumed low-energy cutoff. The energy and spatial distributions of energetic electrons and bremsstrahlung photons bear signatures of the changing density distribution caused by chromospheric evaporation. In particular, the density jump at the evaporation front gives rise to enhanced emission, which, in principle, can be imaged by X-ray telescopes. This model can be applied to investigate a variety of high-energy processes in solar, space, and astrophysical plasmas.

STOCHASTIC ACCELERATION MODEL↗
NASA NTRS2024

Electrostatic Waves and Electron Holes in Simulations of Low-Mach Quasi-Perpendicular Shocks

Collisionless low Mach number shocks are abundant in astrophysical and space plasma environments, exhibiting complex wave activity and wave-particle interactions. In this paper, we present 2D Particle in-Cell (PIC) simulations of quasi-perpendicular nonrelativistic (vsh ≈ (5500−22000) km/s) low Mach number shocks, with a specific focus on studying electrostatic waves in the shock ramp and the precursor regions. In these shocks, an ion-scale oblique whistler wave creates a configuration with two hot counter streaming electron beams, which drive unstable electron acoustic waves (EAWs) that can turn into electrostatic solitary waves (ESWs) at the late stage of their evolution. By conducting simulations with periodic boundaries, we show that EAW properties agree with linear dispersion analysis. The characteristics of ESWs in shock simulations, including their wavelength and amplitude, depend on the shock velocity. When extrapolated to shocks with realistic velocities (vsh ≈ 300 km/s), the ESW wavelength is reduced to one tenth of the electron skin depth and the ESW amplitude is anticipated to surpass that of the quasi-static electric field by more than a factor of 100. These theoretical predictions may explain a discrepancy, between PIC and satellite measurements, in the relative amplitude of high and low-frequency electric field fluctuations.

Plasma astrophysics↗
NASA NTRS1968

Atomic transition probabilities.

Atomic transition probabilities, discussing improvement attributed to wider interest in space science, astrophysics, plasma physics and research technique developments

Garstang, R. H.↗
NASA NTRS1981

An Introduction to Magnetospheric Physics by Means of Simple Models

The large scale structure and behavior of the Earth's magnetosphere is discussed. The model is suitable for inclusion in courses on space physics, plasmas, astrophysics or the Earth's environment, as well as for self-study. Nine quantitative problems, dealing with properties of linear superpositions of a dipole and a constant field are presented. Topics covered include: open and closed models of the magnetosphere; field line motion; the role of magnetic merging (reconnection); magnetospheric convection; and the origin of the magnetopause, polar cusps, and high latitude lobes.

Stern, D. P.↗
NASA NTRS1993

Dust-acoustic double layers - Ion inertial effects

Space and astrophysical plasmas often comprise a number of massive ion components in addition to a tenuous, negatively charged dust component and an electron component. Stationary electrostatic double layers in a dusty plasma are investigated in a model treating the ion components as Boltzmann-distributed (inertialess) fluids. On comparison with the inertialess theory, one finds considerably reduced double layer existence parameter regimes. Significantly, highly nonlinear double layers are ruled out when ion inertia is incorporated. However, in the restricted parameter regimes in which the inertial theory predicts double layers for small ion/dust mass ratios (about 10 exp -15-10 exp -8) there is good qualitative agreement with inertialess theory. The reasons for these, and other discrepancies and similarities, are discussed.

Mace, Richard L.↗
NASA NTRS1992

A new nonlinear diffusion formalism in a magnetized plasma - Application to space physics and astrophysics

A novel diffusion formalism that takes into account the finite width of resonances is presented. The resonance diagram technique is shown to reproduce the details of the particle orbits very accurately, and can be used to determine the acceleration/scattering in the presence of a given wave spectrum. Ways in which the nonlinear orbits can be incorporated into the diffusion equation are shown. The resulting diffusion equation is an extension of the Q-L theory to cases where the waves have large amplitudes and/or are coherent. This new equation does not have a gap at 90 deg in cases where the individual orbits can cross the gap. The conditions under which the resonance gap at 90-deg pitch angle exits are also examined.

Karimbadi, H.↗