Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “MAGNETIC FIELDS”

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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Magnetic Field Effect on the Stability of Flow Induced by a Rotating Magnetic Field

A linear stability analysis has been performed for the flow induced by a rotating magnetic field in a cylindrical column filled with electrically conducting fluid. The first transition is time- independent and results in the generation of Taylor vortices. The critical value of the magnetic Taylor number has been examined as a function of the strength of the transverse rotating magnetic field, the strength of an axial static magnetic field, and thermal buoyancy. Increasing the transverse field increases the critical magnetic Taylor number and decreases the aspect ratio of the Taylor vortices at the onset of instability. An increase in the axial magnetic field also increases the critical magnetic Taylor number but increases the aspect ratio of the Taylor vortices. Thermal buoyancy is found to have only a negligible effect on the onset of instability.

Mazuruk, K.↗
NASA NTRS1999

Magnetic Field Effect on the Stability of Flow Induced by a Rotating Magnetic Field

A linear stability analysis has been performed for the flow induced by a rotating magnetic field in a cylindrical column filled with electrically conducting fluid. The first transition is time-independent and results in the generation of Taylor vortices. The critical value of the magnetic Taylor number has been examined as a function of the strength of the transverse rotating magnetic field, the strength of an axial static magnetic field, and thermal buoyancy. Increasing the transverse field increases the critical magnetic Taylor number and decreases the aspect ratio of the Taylor vortices at the onset of instability. An increase in the axial magnetic field also increases the critical magnetic Taylor number but increases the aspect ratio of the Taylor vortices. Thermal buoyancy is found to have only a negligible effect on the onset of instability.

Mazuruk, K.↗
NASA NTRS1994

A New Approach to Isolating External Magnetic Field Components in Spacecraft Measurements of the Earth's Magnetic Field Using Global Positioning System observables

We review the problem of separating components of the magnetic field arising from sources in the Earth's core and lithosphere, from those contributions arising external to the Earth, namely ionospheric and magnetospheric fields, in spacecraft measurements of the Earth's magnetic field.

magnetic field components ionospheric and magnetos↗
NASA NTRS1979

Spatial distribution of large-scale solar magnetic fields and their relation to the interplanetary magnetic field

The spatial organization of the observed photospheric magnetic field as well as its relation to the polarity of the IMF have been studied using high resolution magnetograms from the Kitt Peak National Observatory. Systematic patterns in the large scale field are due to contributions from both concentrated flux and more diffuse flux. The polarity of the photospheric field, determined on various spatial scales, correlates with the polarity of the IMF. Analyses based on several spatial scales in the photosphere suggest that new flux in the interplanetary medium is often due to relatively small photospheric features which appear in the photosphere up to one month before they are manifest at the earth.

Levine, R. H.↗
NASA NTRS1978

The latitudinal distributions of auroral zone electric fields and ground magnetic perturbations and their response to variations in the interplanetary magnetic field

Measurements of the latitudinal distributions of electric fields obtained with the Chatanika, Alaska, incoherent radar have been employed in determining the influence of the north-south component of the interplanetary magnetic field (IMF) on the electric field pattern. Poleward (or equatorward) shifts produced by the northward (or southward) transitions of the IMF north-south component are given particular attention. The behavior of the electric field patterns and magnetic perturbations in the midnight sector during substorms near the Harang discontinuity is analyzed.

Horwitz, J. L.↗
DOE OSTI2025

Temperature-dependent magnetic-field-induced ab -plane Gd spin reorientations in antiferromagnetic domains in a single crystal of the tetragonal A-type antiferromagnet GdRh 2 Si 2

The compound GdRh 2 Si 2 crystallizes in the body-centered tetragonal ThCr 2 Si 2 structure and exhibits A-type antiferromagnetic order below its Néel temperature T N = 107 K where the Gd moments are ferromagnetically aligned in the ab-plane with the moments in adjacent planes aligned antiferromagnetically. Previously, the nonlinear low-field magnetization versus field M ab ( H ∥ [1, 0, 0]) measurements on single crystals were interpreted in terms of a mean-field model. Here, in this work, we reinterpret this nonlinearity more simply in terms of the response of the ordered moments in four noninteracting tetragonal domains to the applied field and find good agreement with our theory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1983

Two hot, low-field magnetic DA white dwarfs

Two hot stars discovered in the Palomar Green survey which were found to exhibit peculiarly broad and strong Balmer lines possibly indicative of low magnetic fields are discussed. The stars, PG 1658+441 and PG 0136+251, were found to have extended trough-shaped Balmer and Lyman-alpha line profiles when compared to nonmagnetic dwarfs of similar temperatures. Further observations of PG 1658+441 show it to correspond to a 30,000 K pure hydrogen atmosphere and confirm its nature as a magnetic object with a longitudinal field strength of about 0.7 megagauss and a mean surface field of about 2.3 megagauss. PG 0136+251 is found to be a hotter star (40,000-50,000 K) with weaker lines. Although no strong evidence for magnetic line splitting was obtained, it is argued that neither a high surface gravity nor very rapid rotation can account for the Balmer line shapes. Results thus extend the range of magnetic degenerates to include very hot white dwarfs, and demonstrate the usefulness of line-widths as indicators of possible low-field magnetic sources.

Liebert, J.↗
NASA NTRS2008

Performance of a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

While Hall thrusters can operate at high efficiency at kW power levels, it is difficult to construct one that operates over a broad envelope down to 100W while maintaining an efficiency of 45- 55%. Scaling to low power while holding the main dimensionless parameters constant requires a decrease in the thruster channel size and an increase in the magnetic field strength. Increasing the magnetic field becomes technically challenging since the field can saturate the miniaturized inner components of the magnetic circuit and scaling down the magnetic circuit leaves very little room for magnetic pole pieces and heat shields. An alternative approach is to employ a cylindrical Hall thruster (CHT) geometry. Laboratory model CHTs have operated at power levels ranging from the order of 50 Watts up to 1 kW. These thrusters exhibit performance characteristics which are comparable to conventional, annular Hall thrusters of similar size. Compared to the annular Hall thruster, the CHT has a lower insulator surface area to discharge chamber volume ratio. Consequently, there is the potential for reduced wall losses in the channel of a CHT, and any reduction in wall losses should translate into lower channel heating rates and reduced erosion. This makes the CHT geometry promising for low-power applications. Recently, a CHT that uses permanent magnets to produce the magnetic field topology was tested. This thruster has the promise of reduced power consumption over previous CHT iterations that employed electromagnets. Data are presented for two purposes: to expose the effect different controllable parameters have on the discharge and to summarize performance measurements (thrust, Isp, efficiency) obtained using a thrust stand. These data are used to gain insight into the thruster's operation and to allow for quantitative comparisons between the permanent magnet CHT and the electromagnet CHT.

Polzin, Kurt A.↗
NASA NTRS1998

Elementary Theoretical Forms for the Spatial Power Spectrum of Earth's Crustal Magnetic Field

The magnetic field produced by magnetization in Earth's crust and lithosphere can be distinguished from the field produced by electric currents in Earth's core because the spatial magnetic power spectrum of the crustal field differs from that of the core field. Theoretical forms for the spectrum of the crustal field are derived by treating each magnetic domain in the crust as the point source of a dipole field. The geologic null-hypothesis that such moments are uncorrelated is used to obtain the magnetic spectrum expected from a randomly magnetized, or unstructured, spherical crust of negligible thickness. This simplest spectral form is modified to allow for uniform crustal thickness, ellipsoidality, and the polarization of domains by an periodically reversing, geocentric axial dipole field from Earth's core. Such spectra are intended to describe the background crustal field. Magnetic anomalies due to correlated magnetization within coherent geologic structures may well be superimposed upon this background; yet representing each such anomaly with a single point dipole may lead to similar spectral forms. Results from attempts to fit these forms to observational spectra, determined via spherical harmonic analysis of MAGSAT data, are summarized in terms of amplitude, source depth, and misfit. Each theoretical spectrum reduces to a source factor multiplied by the usual exponential function of spherical harmonic degree n due to geometric attenuation with attitude above the source layer. The source factors always vary with n and are approximately proportional to n(exp 3) for degrees 12 through 120. The theoretical spectra are therefore not directly proportional to an exponential function of spherical harmonic degree n. There is no radius at which these spectra are flat, level, or otherwise independent of n.

Voorhies, C.↗
DOE OSTI2025

Demonstrating magnetic field robustness and reducing temporal T1 noise in transmon qubits through magnetic field engineering

The coherence of superconducting transmon qubits is often disrupted by fluctuations in the energy relaxation time (T1), limiting their performance for quantum computing. While background magnetic fields can be harmful to superconducting devices, we demonstrate that both trapped magnetic flux and externally applied static magnetic fields can suppress temporal fluctuations in T1 without significantly degrading its average value or qubit frequency. Using a three-axis Helmholtz coil system, we applied calibrated magnetic fields perpendicular to the qubit plane during cooldown and operation. Remarkably, transmon qubits based on tantalum-capped niobium (Nb/Ta) capacitive pads and aluminum-based Josephson junctions (JJs) maintained T1 lifetimes near 300 μs even when cooled in fields as high as 600 mG. Both trapped flux up to 600 mG and applied fields up to 400 mG reduced T1 fluctuations by more than a factor of two, while higher field strengths caused rapid coherence degradation. We attribute this stabilization to the polarization of paramagnetic impurities, the role of trapped flux as a sink for non-equilibrium quasiparticles (QPs), and partial saturation of fluctuating two-level systems (TLSs). These findings challenge the conventional view that magnetic fields are inherently detrimental and introduce a strategy for mitigating noise in superconducting qubits, offering a practical path toward more stable and scalable quantum systems.

Abdisatarov, Bektur [Fermilab; Jefferson Lab]↗
NASA NTRS1974

High-field magnetization of Dy2O3

The magnetization of powdered samples of Dy2O3 has been measured at temperatures between 1.45 deg and 4.2 K, in applied magnetic fields ranging to 7 Teslas. A linear dependence of magnetization on applied field is observable in high field region, the slope of which is independent of temperature over the range investigated. The extrapolated saturation magnetic moment is 2.77 + or - 0.08 Bohr magnetons per ion.

Flood, D. J.↗
NASA NTRS1974

High-field magnetization of Dy2O3

The magnetization of powdered samples of Dy2O3 has been measured at temperatures between 1.45 and 4.2 K, in applied magnetic fields ranging to 70 kilogauss. A linear dependence of magnetization on applied field is observable in the high-field region, the slope of which is independent of temperature over the range investigated. The extrapolated saturation magnetic moment is about 2.77 Bohr magnetons per ion.

Flood, D. J.↗
DOE OSTI2023

Effect of printing parameters on 3D-printed carbon fiber-reinforced polymer composites under magnetic field control

Magnetic field controlled (MFC) 3D printing is a promising method for realizing the intelligent control of the structural performance of carbon fiber-reinforced plastic (CFRP) composites by adjusting the fiber orientation during the printing process. However, few studies have focused on the influence of the printing parameters on the magnetic control of the fiber direction. Therefore, in this study, the mechanical properties and internal fiber distributions of MFC 3D-printed samples of CFRP composites with 10 wt% fiber content, which were printed at different speeds and layer thicknesses, were investigated. Subsequently, the effects of the fiber content on the mechanical properties and fiber distribution of the MFC 3D-printed samples were studied. Furthermore, the origin of fiber fracture was evaluated through observation and analysis of the fracture section using scanning electron microscopy. The fiber orientation could be well adjusted under the action of a magnetic field and adjustment of printing parameters, thereby improving the tensile strength, young's modulus significantly with slightly decrease of fracture elongation. The recommended parameter combinations (printing speed and layer thickness) were 40 mm/s and 0.2 mm for 10 wt% fiber content CFRP composites.

36 MATERIALS SCIENCE↗