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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Magnetic holes in the solar wind

An analysis of high-resolution magnetic field measurements from the Goddard Space Flight Center magnetometer on Explorer 43 showed that low magnetic field intensities (less than 1 gamma) in the solar wind at 1 AU occur as distinct depressions, or 'holes', in otherwise nearly average conditions. These magnetic holes are new kinetic scale phenomena, having a characteristic dimension of the order of 20,000 km. They occurred at a rate of 1.5/d in the 18-day interval (March 18 to April 6, 1971) that was considered. Most magnetic holes are characterized by both a depression in /B/ and a change in the magnetic field direction, and some of these are possibly the result of magnetic merging. However, in other cases the direction, does not change; such holes are not due to merging but might be a diamagnetic effect due to localized plasma inhomogeneities.

Turner, J. M.↗
NASA NTRS1975

On the apparent diamagnetism of the lunar environment in the geomagnetic tail lobes

The reported investigation presents the magnetic observations averaged in a format that facilitates comparison with models of plasma diamagnetic effects. These models demonstrate that a decreased plasma energy density in the lunar vicinity always causes an induced dipole that increases the external field. Hence, an increased plasma energy density in the lunar environs is required to account for the observed magnetic decrease. There are several different plasma populations in the high-latitude geomagnetic tail lobes, including the lunar ions resulting from photoionization of lunar atmosphere neutrals, possible fluxes of polar-wind protons, low-energy particle events which consist of antisolar directed fluxes of 100-eV protons, photoelectrons from the dayside lunar surface, and a high-energy thermal population.

Goldstein, B. E.↗
NASA NTRS1979

Electromagnetic structure of the magnetopause and boundary layer

After a review of the properties and predictions of the closed and open models of the magnetopause, OGO-5 magnetometer data are used to illustrate various observed signatures of the magnetopause current layer and the adjacent plasma boundary layer. Among the topics touched upon are: fluctuations, diamagnetic effects, and field aligned currents in the boundary layer; one dimensionality of the magnetopause; presence and absence of a magnetic field component perpendicular to the magnetopause; finite ion gyroradius effects. A brief summary is given of existing Vlasov theory for the description of tangential, rotational, and contact discontinuities. Special attention is paid to the tangential momentum balance and the jump conditions at a rotational discontinuity. Low frequency fluctuations are discussed with emphasis on the signatures of the tearing mode.

Sonnerup, B. U. O.↗
NASA NTRS2008

New Understanding of Mercury's Magnetosphere from MESSENGER'S First Flyby

Observations by the MESSENGER spacecraft on 14 January 2008 have revealed new features of the solar system's smallest planetary magnetosphere. The interplanetary magnetic field orientation was unfavorable for large inputs of energy from the solar wind and no evidence of magnetic substorms, internal magnetic reconnection, or energetic particle acceleration was detected. Large-scale rotations of the magnetic field were measured along the dusk flank of the magnetosphere and ultra-tow frequency waves were frequently observed beginning near closest approach. Outbound the spacecraft encountered two current-sheet boundaries across which the magnetic field intensity decreased in a step-like manner. The outer current sheet is the magnetopause boundary. The inner current sheet is similar in structure, but weaker and -1000 km closer to the planet. Between these two current sheets the magnetic field intensity is depressed by the diamagnetic effect of planetary ions created by the photo-ionization of Mercury's exosphere.

Slavin, James A.↗
NASA NTRS2008

The Structure of the Electron Outflow Jet in Collisionless Magnetic Reconnection

Particle-in-cell simulations and analytic theory are applied to the study of the electron outflow jet in collisionless magnetic reconnection. In these jets, which have also been identified in spacecraft observations, electron flow speeds in thin layers exceed the ExB drift, suggesting that electrons are unmagnetized. In this study, we find the surprising result that the electron flow jets can be explained by a combination of EjcB drifts and of diamagnetic effects, through the combination of the gradients of particle pressure and of the magnetic field. In a suitably rotated coordinate system, the electron motion is readily decomposed into ExB drift and the motion to support the required current density, consistent with electron gyrotropy. This process appears to be nondissipative.

Hesse, Michael↗
DOE OSTI2020

Two-fluid and kinetic transport physics of Kelvin–Helmholtz instabilities in nonuniform low-beta plasmas

Hall-magnetohydrodynamic (Hall-MHD) theory, two-fluid simulations, and kinetic simulations are used in this work to investigate the cross-field transport properties of Kelvin–Helmholtz instabilities in nonuniform low-beta collisionless plasmas. Hall-MHD analysis shows how the linear properties of the instability are modified by density gradients and magnetization. High-order accurate two-fluid and kinetic simulations, with complete dynamics of finite-mass electrons and ions, are applied to a suite of parameter cases to systematically assess the effects of diamagnetic drift, magnetization, charge separation, and finite Larmor motion. Initialization of exact two-species kinetic equilibria facilitates the study of isolated physical effects and enables detailed cross-comparisons between two-fluid and kinetic simulations, including for cases where ion gyroradii are comparable to gradient scale lengths. For nonuniform plasmas with significant space charge, the results of two-fluid and kinetic simulations are found to disagree with Hall-MHD predictions. Kelvin–Helmholtz instability growth rates, per unit shear, are shown to be smaller when ion diamagnetic drift and $E \times B$ drift are parallel and larger when the two drifts are antiparallel. The effect is attributed to polarization drift in the shear layer, which leads to redistribution of charge, alters the electric field that drives plasma advection, and consequently modifies growth rates. Instability-induced mass transport for different parameters is characterized in terms of the flux across the shear layer and a simplified diffusion model. Distribution functions from kinetic simulations are shown to deviate substantially from Maxwellian reconstructions, indicating the importance of kinetic physics during the nonlinear phase of the instability.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1992

Observation and theory of the barium releases from the CRRES satellite

The relationship between releases of barium from the NASA Combined Release and Radiation Effects Satellite (CRRES) and enhanced auroral activity is discussed with reference to observational data. Barium releases were conducted at a variety of altitudes and injection velocities, and plasma irregularities are reported as a result of the interactions. Auroral activity increased within 5 min of each release, and references are made to the effects on diamagnetic cavities, bulk ion motion, and stimulated electron and ion precipitation. Artificially created structured diamagnetic cavities are noted for each release, plasma waves are generated by the high-speed ion clouds, and enhanced ionization is found in the critical ionization-velocity process. Barium releases are effective in stimulating electron precipitation, and the observed irregularities are related to cycloid bunching of the initial ion distributions.

Bernhardt, P. A.↗
NASA NTRS2000

Magnetic Susceptibility Effects and Lorentz Damping in Diamagnetic Fluids

A great number of crystals (semi-conductor and protein) grown in space are plagued by convective motions which contribute to structural flaws. The character of these instabilities is not well understood but is associated with density variations in the presence of residual gravity and g-jitter. Both static and dynamic (rotating or travelling wave) magnetic fields can be used to reduce the effects of convection in materials processing. In semi-conductor melts, due to their relatively high electrical conductivity, the induced Lorentz force can be effectively used to curtail convective effects. In melts/solutions with reduced electrical conductivity, such as aqueous solutions used in solution crystal growth, protein crystal growth and/or model fluid experiments for simulating melt growth, however, the variation of the magnetic susceptibility with temperature and/or concentration can be utilized to better damp fluid convection than the Lorentz force method. This paper presents a comprehensive, comparative numerical study of the relative damping effects using static magnetic fields and gradients in a simple geometry subjected to a thermal gradient. The governing equations are formulated in general terms and then simplified for the numerical calculations. Operational regimes, based on the best damping technique for different melts/solutions are identified based on fluid properties. Comparisons are provided between the numerical results and available results from experiments in surveyed literature.

Ramachandran, Narayanan↗
DOE OSTI2023

MAS: A versatile Landau-fluid eigenvalue code for plasma stability analysis in general geometry

We have developed a new global eigenvalue code, Multiscale Analysis for plasma Stabilities (MAS), for studying plasma problems with wave toroidal mode number (n) and frequency (ω) in a broad range of interest in general tokamak geometry, based on a five-field Landau-fluid description of thermal plasmas. Beyond keeping the necessary plasma fluid response, we further retain the important kinetic effects including diamagnetic drift, ion finite Larmor radius, finite parallel electric field (E||), ion and electron Landau resonances in a self-consistent and non-perturbative manner without sacrificing the attractive efficiency in computation. The physical capabilities of the code are evaluated and examined in the aspects of both theory and simulation. In theory, the comprehensive Landau-fluid model implemented in MAS can be reduced to the well-known ideal MHD model, electrostatic ion-fluid model, and drift-kinetic model in various limits, which clearly delineates the physics validity regime. In simulation, MAS has been well benchmarked with theory and other gyrokinetic and kinetic-MHD hybrid codes in a manner of adopting the unified physical and numerical framework, which covers the kinetic Alfv\'en wave (KAW), ion sound wave (ISW), low-n kink, high-n ion temperature gradient mode (ITG) and kinetic ballooning mode (KBM). Moreover, MAS is successfully applied to model the Alfv\'en eigenmode (AE) activities in DIII-D discharge #159243, which faithfully captures the frequency sweeping of reversed shear Alfv\'en eigenmode (RSAE), the tunneling damping of toroidal Alfv\'en eigenmode (TAE), as well as the polarization characteristics of kinetic beta-induced Alfv\'en eigenmode (KBAE) and beta-induced Alfv\'en-acoustic eigenmode (BAAE) being consistent with former gyrokinetic theory and simulation. With respect to the key progress contributed to the community, MAS has the advantage of combining rich physics ingredients, realistic global geometry and high computation efficiency together for plasma stability analysis in linear regime.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2003

Models And Experiments Of Laminar Diffusion Flames In Non-Uniform Magnetic Fields

Non-uniform magnetic fields affect laminar diffusion flames as a result of the paramagnetic and diamagnetic properties of the products and reactants. Paramagnetism is the weak attraction to a magnetic field a material exhibits as a result of permanent magnetic dipole moments in the atoms of the material. Diamagnetism is the weak repulsion to a magnetic field exhibited by a material due to the lack of permanent magnetic dipole moments in the atoms of a material. The forces associated with paramagnetic and diamagnetism are several orders of magnitude less than the forces associated with the more familiar ferromagnetism. A typical example of a paramagnetic gas is oxygen while hydrocarbon fuels and products of combustion are almost always diamagnetic. The fact that magnets can affect flame behavior has been recognized for more than one hundred years. Early speculation was that such behavior was due to the magnetic interaction with the ionized gases associated with a flame. Using a scaling analysis, it was later shown that for laminar diffusion flames the magnetic field/ionized gas interaction was insignificant to the paramagnetic and diamagnetic influences. In this effort, the focus has been on examining laminar diffusion slot flames in the presence of non-uniform upward decreasing magnetic fields produced using permanent magnets. The principal reason for choosing slot flames was mathematical models of such flames show an explicit dependence on gravitational body forces, in the buoyancy-controlled regime, and an applied magnetic field would also impose a body force. In addition, the behavior of such flames was more easily visualized while maintaining the symmetry of the two-dimensional problem whereas it would have been impossible to obtain a symmetric magnetic field around a circular flame and still visually record the flame height and shape along the burner axis. The motivation for choosing permanent magnets to produce the magnetic fields was the assumption that space-related technologies based on the knowledge gained during this investigation would more likely involve permanent magnets as opposed to electromagnets. While no analysis has been done here to quantify the impact that an electric field, associated with an electromagnetic, would have relative to the paramagnetic and diamagnetic interactions, by using permanent magnets this potential effect was completely eliminated and thus paramagnetic and diamagnetic effects were isolated.

Baker, J.↗
DOE OSTI2023

Gyrokinetic simulations of electrostatic microturbulence in ADITYA-U tokamak

Global gyrokinetic simulations of the electrostatic microturbulence driven by the pressure gradients of thermal ions and electrons are carried out for the ADITYA-U tokamak geometry using its experimental plasma profiles and with collisional effects. The dominant instability is trapped electron mode (TEM) based on the linear eigenmode structure and its propagation in the electron diamagnetic direction. Collisional effects suppress turbulence and transport to a certain extent. Zonal flow is not playing a critical role in the TEM saturation, which is dominated by the inverse cascade. The frequency spectrum of the electrostatic fluctuations is in broad agreement with the experimentally recorded spectrum in the ADITYA-U, with a bandwidth ranging from ~0 to 50 kHz.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1991

Meissner-Effect Stepping Motor

Proposed stepping motor derives torque from diamagnetic repulsion produced by Meissner effect - exclusion of magnetic field from interior of superconductor. Design of motor takes advantage of silver-doped YB2Cu3O and other compounds superconductive at temperatures as high as that of liquid nitrogen. Skin of rotor cooled below its superconducting-transition temperature by liquid nitrogen. O-rings prevent leaks of liquid nitrogen from rotor. Weight, cost, and maintenance reduced.

Robertson, Glen A.↗
NASA NTRS1990

Superconductivity in 2-2-3 Y2Ba2Cu3O(sub 8+ delta)

Researchers synthesized a new high T(sub c) 2-2-3 superconductor (Y2Ba2Cu3O8+delta) by a special preparation technique and characterized it by ac-susceptibility measurements. Diamagnetism and Meissner effect sets in at low fields and superconducting transition onsets at 90 K. The systematic investigation of the real and imaginary components of ac-susceptibility as a function of temperature and applied ac magnetic field reveals that the magnetic behavior is that of a granular type superconductor.

Joshi, H. H.↗
NASA NTRS1991

Superconductivity in 2-2-3 system Y2Ba2Cu2O(8+delta)

Researchers synthesized a new high T(sub c) 2-2-3 superconductor Y2Ba2Cu3O(8+delta) by a special preparation technique and characterized it by ac-susceptibility measurements. Diamagnetism and Meissner effect sets in at low fields and superconducting transition onsets at 90 K. The systematic investigation of the real and imaginary components of ac-susceptibility as a function of temperature and applied ac magnetic field reveals that the magnetic behavior is that of a granular type superconductor.

Joshi, H. H.↗
DOE OSTI2022

Magnetic Control of Soft Chiral Phonons in PbTe

We report PbTe crystals have a soft transverse optical phonon mode in the terahertz frequency range, which is known to efficiently decay into heat-carrying acoustic phonons, resulting in anomalously low thermal conductivity. Here, we studied this phonon via polarization-dependent terahertz spectroscopy. We observed softening of this mode with decreasing temperature, indicative of incipient ferroelectricity, which we explain through a model including strong anharmonicity with a quartic displacement term. In magnetic fields up to 25 T, the phonon mode splits into two modes with opposite handedness, exhibiting circular dichroism. Their frequencies display Zeeman splitting together with an overall diamagnetic shift with increasing magnetic field. Using a group-theoretical approach, we demonstrate that these observations are the result of magnetic field-induced morphic changes in the crystal symmetries through the Lorentz force exerted on the lattice ions. Thus, our Letter reveals a novel process of controlling phonon properties in a soft ionic lattice by a strong magnetic field.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Identification of a window for quiescent H-mode operation in MHD stability diagram of DIII-D plasmas

A window for quiescent H-mode (QH-mode) operation in DIII-D plasmas in the diagram of pedestal magnetohydrodynamic (MHD) stability was identified through linear MHD stability analysis, accounting for the effects of plasma rotation and ion diamagnetic drift. The operation window lies between the stability boundaries of the kink/peeling mode (K/PM) identified with and without the inclusion of plasma rotation effects. In this region, the mode remains unstable unless rotation effects are considered alongside the ion diamagnetic drift, which is consistently included in the analysis. The stabilization of the MHD mode, facilitated by the coupled effects of plasma rotation and ion diamagnetic drift, plays a crucial role in widening the window, enabling the attainment of the QH-mode state. Furthermore, the suppression of edge localized modes (ELM) can be achieved by controlling the pedestal structure to ensure the plasma state remains within the operation window. The location of the operation window in the stability diagram depends on the K/PM stability properties. Therefore, optimizing conditions for QH-mode requires adjustments based on changes in stability characteristics. A pressure pedestal and its associated bootstrap current density near the last closed flux surface are advantageous for situating the plasma state within the window. However, excessive current density can trigger ELMs. This trend was confirmed through comparisons of MHD stability diagrams between QH-mode and ELMy H-mode plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Impact of impurities on peeling–ballooning modes and turbulence in tokamak plasmas

This study investigates the impact of various impurity species on peeling–ballooning (PB) modes and microturbulence in tokamak plasmas through the extension of traditional two-fluid and gyro-landau-fluid (GLF) models. By incorporating finite Larmor radius (FLR) effects, the analysis provides a comprehensive understanding of impurity-driven impact and its interaction with plasma turbulence. Depending on charge state and local plasma conditions, heavy impurities may exhibit gyro-radii larger than those of main ions, which are captured in the extended GLF model presented. Following the presentation of modified two-fluid equations incorporating impurity effects, we systematically analyze the distinctions between impurity and main ion dynamics and their resultant feedback mechanisms on plasma behavior. Derivation of the linear dispersion relation enables quantification of impurity-mediated modifications to: plasma vorticity, diamagnetic drift and gyroviscous effects, electron Hall physics, and FLR effects. BOUT++ – based linear simulations corroborate this formalism, demonstrating systematic stabilization of PB modes upon impurity seeding. And then operational implications for practical impurity control strategies in tokamak devices are proposed. The results underscore the necessity of impurity management to maintain stability and optimize plasma confinement, with specific focus on how FLR effects contribute to transport dynamics. This work paves the way for enhanced modeling and simulation efforts, supporting the development of strategies to control impurity-induced turbulence and improve overall reactor performance.

BOUT++ simulation↗
DOE OSTI2022

Modeling study of divertor particle and heat flux asymmetries for EAST H-mode discharges

The BOUT++ transport code is run to study the effects of plasma drifts on the divertor out-in asymmetries (DOIAs) of particle and heat fluxes and their decay widths for EAST lower single null H-mode discharges. The diamagnetic drift seems to have no effects on the DOIAs of total particle and heat fluxes due to its divergence-free nature. However, it could significantly increase the DOIAs of peak particle and heat fluxes and the flux decay widths. The E × B drift is found to induce a large plasma flow to the divertor region, enhancing the DOIAs of both total and peak particle and heat fluxes and the flux decay widths. Both the radial and poloidal components of the E × B drift are necessary in increasing the DOIAs, however, the radial E × B drift seems to play a more important role. The effects on the DOIAs caused by both diamagnetic and E × B drifts are reversed with the reverse of toroidal magnetic field. The heat flux decay width λ q and spreading width S q are important physical and engineering parameters for the divertors and could be obtained by fitting the heat flux profiles at divertor targets. The λ q at the outer target from the simulation case with all drifts could well match with the multi-machine scaling proposed by Eich and the DOIA of λ q is in reasonable agreement with the scaling proposed by Goldston.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗