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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Measurements of the lunar induced magnetic moment in the geomagnetic tail - Evidence for a lunar core

Apollo 15 and 16 subsatellite fluxgate magnetometer data have been analyzed for all intervals in which the moon was in the lobes of the geomagnetic tail to obtain an improved estimate of the average magnitude of the induced dipole moment of the moon. The resulting set of estimates yields an induced magnetic moment of -4.23 x 10 to the 22nd Gauss-cu cm per Gauss of applied field, corresponding to a G-factor of -0.008 + or - 0.001. These measurements do not place strong constraints on the conductivity of the lunar core. The observed effects would be detected as long as the core conductivity was greater than about 10 mho/m. If the outer cool layers of the moon that are at temperatures below the effective Curie point contain little or no free iron, then these measurements are consistent with the presence of a conducting core whose radius is slightly larger than 400 km. If these outer layers of the moon contain significant amounts of free iron and hence exhibit the paramagnetism expected in such a situation the core size could be even greater.

Russell, C. T.↗
NASA NTRS2002

The Permanent and Inductive Magnetic Moments of Ganymede

Data acquired by the Galileo magnetometer on five passes by Ganymede have been used to characterize Ganymede's internal magnetic moments. Three of the five passes were useful for determination of the internal moments through quadrupole order. Models representing the internal field as the sum of dipole and quadrupole terms or as the sum of a permanent dipole field upon which is superimposed an induced magnetic dipole driven by the time varying component of the externally imposed magnetic field of Jupiter's magnetosphere give equally satisfactory fits to the data. The permanent dipole moment has an equatorial field magnitude 719 nT and is tilted by 176 degrees from the spin axis with the pole in the southern hemisphere rotated by 24 degrees from the Jupiter-facing meridian plane towards the trailing hemisphere. The data are consistent with an inductive response of a good electrical conductor of radius approximately 1 Ganymede radius. Although the data do not enable us to establish the presence of an inductive response beyond doubt, we favor the inductive response model because it gives a good fit to the data using only 4 parameters to describe the internal sources of fields, whereas the equally good dipole plus quadrupole fit requires 8 parameters. An inductive response is consistent with a buried conducting shell, probably liquid water with dissolved electrolytes, somewhere in the first few hundred km below Ganymede's surface. The depth at which the ocean is buried beneath the surface is somewhat uncertain, but our favored model suggests a depth of order 150 kilometers. As both temperature and pressure increase with depth and the melting temperature of pure ice decreases to a minimum at approximately 170 kilometer depth, it seems possible that near this location, a layer of water would be sandwiched between layers of ice.

Kivelson, M. G.↗
DOE OSTI2025

Run 2/3 measurement of the muon anomalous magnetic moment by the Muon g-2 experiment at Fermilab

The Muon g-2 experiment at Fermilab seeks to measure the muon magnetic moment anomaly, $a_μ=(g-2)/2$, with a final target precision of 0.14 parts-per-million (ppm). The experiment's initial result, published in 2021 using Run 1 data from 2018, confirmed the previous measurement at Brookhaven National Laboratory with a comparable sensitivity of 0.46 ppm. In 2023, a new result based on Run 2 and Run 3 data, collected in 2019 and 2020, was released. These datasets contain four times the data from Run 1, significantly enhancing sensitivity and achieving an unprecedented uncertainty of 0.20 ppm. This advancement resulted in a two-fold improvement in both statistical and systematic uncertainties. Here, we will discuss the muon $g-2$ measurement, the increased precision relative to the Run 1 result, and provide an outlook on future measurements which will incorporate datasets from 2021 to 2023. Additionally, we will explore the implications of comparing the new measurements with the latest Standard Model predictions for muon g-2.

Zaid, Estifa'a [Liverpool U.]↗
NASA NTRS1987

Revised upper limit on the internal magnetic moment of Venus

Over four Venus years of low altitude nightside PVO magnetometer observations are used to establish a new upper limit for the magnetic moment of Venus. Improvements over previous studies include data coverage and new instrument calibration information. The upper limit on an internal dipole moment is determined to be 8.4 x 10 to the 10th T cu m.

Phillips, J. L.↗
NASA NTRS1976

The magnetic moment of Venus - Venera-4 measurements reinterpreted

Venera-4 magnetic-field measurements made during that spacecraft's descent through the atmosphere of Venus are reexamined using three models for the interaction of the solar-wind with the planet. The first model assumes the existence of just the interplanetary and planetary magnetic fields; the second admits the presence of a magnetosheath and a current layer, but assumes that the magnetosheath field is spatially uniform between the planet and the bow shock; the third assumes shielding of the planetary field from the magnetosheath field by a current layer. All three models are found to yield a strong altitude dependence for the magnitude of the planetary field, suggesting that the intrinsic magnetic dipole moment of Venus may exceed that of both Mars and Mercury. It is concluded that a Venusian surface field of 30 gammas is a plausible interpretation of the Venera-4 measurements.-

Russell, C. T.↗
NASA NTRS1985

Remote sensing of the magnetic moment of Uranus - Predictions for Voyager

The current understanding of the power transfer mechanisms by which power is supplied to a planet's magnetosphere by the kinetic energy of planetary spin and the energy flux of the impinging solar wind is applied to the case of Uranus, in order to predict the detectability of radio and auroral emissions by the planetary radio astronomy (PRA) and UV spectrometer (UVS) instruments of the Voyager spacecraft. The power available for the two energy transfer phenomena cited is a function of Uranus' magnetic moment, which is presently derived for each power source as a function of the date of first detection of radio emissions by the PRA or auroral emissions by the UVS.

Hill, T. W.↗
DOE OSTI2024

Detailed report on the measurement of the positive muon anomalous magnetic moment to 0.20 ppm

We present details on a new measurement of the muon magnetic anomaly, a μ =(g μ −2)/2. The result is based on positive muon data taken at Fermilab’s Muon Campus during the 2019 and 2020 accelerator runs. The measurement uses 3.1 GeV/c polarized muons stored in a 7.1-m-radius storage ring with a 1.45 T uniform magnetic field. The value of a μ is determined from the measured difference between the muon spin precession frequency and its cyclotron frequency. This difference is normalized to the strength of the magnetic field, measured using nuclear magnetic resonance. The ratio is then corrected for small contributions from beam motion, beam dispersion, and transient magnetic fields. We measure a μ =116592057(25)×10 −11 (0.21 ppm). This is the world’s most precise measurement of this quantity and represents a factor of 2.2 improvement over our previous result based on the 2018 dataset. In combination, the two datasets yield a μ (FNAL)=116592055(24)×10 −11 (0.20 ppm). Combining this with the measurements from Brookhaven National Laboratory for both positive and negative muons, the new world average is a μ (exp)=116592059(22)×10 −11 (0.19 ppm).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Final Report on the Measurement of the Positive Muon Anomalous Magnetic Moment at Fermilab to 127 ppb

This report details the final measurement of the muon magnetic anomaly, $a_μ=(g_μ-2)/2$, by the Muon $g-2$ experiment at Fermi National Accelerator Laboratory (FNAL), using positive muons collected from 2021 to 2023. The value of $a_μ$ is determined from the ratio of the anomalous spin precession frequency to the shielded proton precession frequency in the muon storage ring magnetic field, combined with external constants known at the 22 ppb level. The new dataset, containing over $2.5$ times the statistics of our previous results, yields $a_μ=116\,592\,0710(162)\times 10^{-12}$ (139 ppb), or $a_μ=116\,592\,0705(148)\times 10^{-12}$ (127 ppb) when combined with our previous results. The new experimental world average, dominated by the measurements at FNAL, is $a_μ^{\text{Exp}}=116\,592\,0715(145)\times 10^{-12}$ (124 ppb).

Aguillard, D. P. [U. Michigan, Ann Arbor] (ORCID:0↗
DOE OSTI2025

Diffusion Quantum Monte Carlo Benchmarking of Magnetic Moments in MnBi 2 Te 4

The intrinsically antiferromagnetic topological insulator, MnBi 2 Te 4 (MBT), has garnered significant attention recently due to its potential to host numerous exotic topological quantum states. Unfortunately, their consistent realization has been hindered by intrinsic antisite defects among the Mn and Bi sublattices. In this work, we establish Mn magnetization of pristine MBT through high level diffusion Monte Carlo calculations, which can serve as a precise starting point for various models to estimate antisite defect concentrations in actual MBT samples. The benchmark quality of DMC calculations is further identified from out model estimating antisite defect concentrations, which combines the benchmarked Mn magnetization with data from magnetic susceptibility and intermediate field magnetization measurements. This reproduces well Bi Mn and Mn Bi concentrations measured in the experiments. Here, we anticipate these theoretically based magnetic purity measures may be used as minimization targets in cycles of refinement to synthesize MBT with low antisite defect concentrations and more reproducible topological properties.

Defects↗
NASA NTRS1982

An assessment of the performance of the Spanwise Iron Magnet rolling moment generating system for magnetic suspension and balance systems using the finite element computer program GFUN

The development of a powerful method of magnetic roll torque generation is essential before construction of a large magnetic suspension and balance system (LMSBS) can be undertaken. Some preliminary computed data concerning a relatively new dc scheme, referred to as the spanwise iron magnet scheme are presented. Computations made using the finite element computer program 'GFUN' indicate that adequate torque is available for at least a first generation LMSBS. Torque capability appears limited principally by current electromagnet technology.

Britcher, C. P.↗
NASA NTRS1983

Magnetic dipole moment estimates for an ancient lunar dynamo

The four measured planetary magnetic moments combined with a recent theoretical prediction for dynamo magnetic fields suggests that no dynamo exists in the moon's interior today. For the moon to have had a magnetic moment in the past of sufficient strength to account for at least some of the lunar rock magnetism, the rotation would have been about twenty times faster than it is today and the radius of the fluid, conducting core must have been about 750 km. The argument depends on the validity of the Busse solution to the validity of the MHD problem of planetary dynamos.

Anderson, K. A.↗
NASA NTRS1974

The permanent and induced magnetic dipole moment of the moon

Magnetic field observations with the Apollo 15 subsatellite have been used to deduce the components of both the permanent and induced lunar dipole moments in the orbital plane. The present permanent lunar magnetic dipole moment in the orbital plane is less than 1.3 times ten to the eighteenth power gauss-cu cm. Any uniformly magnetized near surface layer is therefore constrained to have a thickness-magnetization product less than 2.5 emu-cm per g. The induced moment opposes the external field, implying the existence of a substantial lunar ionosphere with a permeability between 0.63 and 0.85. Combining this with recent measures of the ratio of the relative field strength at the ALSEP and Explorer 35 magnetometers indicates that the global lunar permeability relative to the plasma in the geomagnetic tail lobes is between 1.008 and 1.03.

Russell, C. T.↗
NASA NTRS1972

Magnetic dipole moment determination by near-field analysis

A method for determining the magnetic moment of a spacecraft from magnetic field data taken in a limited region of space close to the spacecraft. The spacecraft's magnetic field equations are derived from first principles. With measurements of this field restricted to certain points in space, the near-field equations for the spacecraft are derived. These equations are solved for the dipole moment by a least squares procedure. A method by which one can estimate the magnitude of the error in the calculations is also presented. This technique was thoroughly tested on a computer. The test program is described and evaluated, and partial results are presented.

Eichhorn, W. L.↗
NASA NTRS1990

Speculation on a Solar Chronometer for Climate

Solar activity has been correlated to climatic fluctuations and has been postulated as a major factor in quasi-periodic global climatic change. However, correlations are not explanations of physical mechanisms and do not couple cause with effect. A mechanism for a chronometer for solar output variability is proposed based on relations between properties of thermonuclear fusion, nuclear magnetic moment, and nuclear magnetic resonance. A fundamental oscillation of a nucleus with a net nuclear magnetic moment (NMM) is the precession of its axis of rotation when subjected to a magnetic field. Nuclear magnetic resonance (NMR) is the preferred frequency of precession for a nucleus of a particular isotope when placed in a magnetic field of specific intensity. The NMM for those isotopes involved in the proton-proton (p-p) chain pathway for solar fusion varies from strong positive to strong negative. Individual fusion events, for hydrogen and helium isotopes which release varying amounts of energy, may be controlled by NMR frequencies. The pulses of energy from fusion events occurring at NMR frequencies in the solar interior may be transformed into pressure or gravity waves that emerge as gravity or acoustic waves at the surface. Dictated by spherical harmonics, certain wavelengths may be reinforced and reenter the solar interior to modulate the fusion process. Qualitative analysis of solar and climatic data support the interaction of the three basic components of the chronometer, magnetic activity, oscillation frequency, and solar energy output.

Perry, Charles A.↗