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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Two-dimensional noncommutative atom gas with the Anandan interaction

Landau-like quantization of the Anandan system in a special electromagnetic field is studied. Unlike the cases of the Aharonov-Casher (AC) system and the He-McKellar-Wilkens (HMW) system, the torques of the system on the magnetic dipole and the electric dipole do not vanish. By constructing Heisenberg algebra, the Landau analog levels and eigenstates on commutative space, noncommutative (NC) space, and NC phase space are obtained, respectively. By using the coherent state method, some statistical properties of such free-atom gas are studied and the expressions of some thermodynamic quantities related to revolution direction are obtained. Two particular cases of temperature are discussed and the more simple expressions of the free energy on the three spaces are obtained. We give the relation between the value of {sigma} and revolution direction clearly and find Landau like levels of the Anandan system are invariant and the levels between the AC system and the HMW system are interchanged each other under Maxwell dual transformations on the three spaces. The two sets of eigenstates labeled by {sigma} can be related by a supersymmetry transformation on commutative space, but the phenomenon do not occur on NC situation. We emphasize that some results relevant to Anandan interaction are suitable for the cases of AC interaction and HMW interaction under special conditions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Low-lying structure of neutron-rich Zn and Ga isotopes

Low-lying states of even-even Zn and odd-mass Ga nuclei with neutron numbers between 42 and 50 have been calculated within the framework of the SDG-pair approximation of the nuclear shell model. We employ a monopole and quadrupole pairing plus quadrupole-quadrupole interaction with optimized parameters, which are assumed to be constants for nuclei with the same proton number or neutron number. We calculate low-lying level schemes, electric quadrupole and magnetic dipole moments, and E2 and M1 transition rates. Reasonable agreement is achieved between the calculated results and experimental data. Dominant configurations in the ground states of odd-mass Ga nuclei are discussed in terms of pair correlations. The weak-coupling picture for some states of odd-mass Ga nuclei is studied.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Magnonic Floquet Hofstadter butterfly

We introduce the magnonic Floquet Hofstadter butterfly in the two-dimensional (2D) insulating honeycomb ferromagnet using a combination of spin wave theory and quantum field theory. We show that hopping magnetic dipole moment (i.e. magnon quasiparticles) in the 2D insulating honeycomb ferromagnet accumulates the Aharonov–Casher phase when irradiated by an oscillating space- and time-dependent electric field. We study two different cases. In the first case, we consider the effects of only space-dependent electric field. In this case, we realize the magnonic Hofstadter spectrum with similar fractal structure as graphene subject to a perpendicular magnetic field, but with no spin degeneracy due to broken time-reversal symmetry by the ferromagnetic order. In addition, the magnonic Dirac points and Landau levels occur at finite energy as expected in a bosonic system. Remarkably, this discrepancy does not affect the topological invariant of the system. Consequently, the magnonic Chern number assumes odd values and the magnon Hall conductance gets quantized by odd integers. In the second case, we study the effects of both space- and time-dependent electric field. In this case, the theoretical framework is studied by the Floquet formalism. We show that the magnonic Floquet Hofstadter spectrum emerges entirely from the oscillating space- and time-dependent electric field, which is in stark contrast to electronic Floquet Hofstadter spectrum, where irradiation by circularly polarized light and a perpendicular magnetic field are applied independently. We study the deformation of the fractal structure at different laser frequencies and amplitudes, and analyze the topological phase transitions associated with gap openings in the magnonic Floquet Hofstadter butterfly.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Spin-rotation and NMR shielding constants in HCl

The spin-rotation and nuclear magnetic shielding constants are analysed for both nuclei in the HCl molecule. Nonrelativistic ab initio calculations at the CCSD(T) level of approximation show that it is essential to include relativistic effects to obtain spin-rotation constants consistent with accurate experimental data. Our best estimates for the spin-rotation constants of {sup 1}H{sup 35}Cl are C{sub Cl} = −53.914 kHz and C{sub H} = 42.672 kHz (for the lowest rovibrational level). For the chlorine shielding constant, the ab initio value computed including the relativistic corrections, σ(Cl) = 976.202 ppm, provides a new absolute shielding scale; for hydrogen we find σ(H) = 31.403 ppm (both at 300 K). Combining the theoretical results with our new gas-phase NMR experimental data allows us to improve the accuracy of the magnetic dipole moments of both chlorine isotopes. For the hydrogen shielding constant, including relativistic effects yields better agreement between experimental and computed values.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Noniterative finite amplitude methods for E 1 and M 1 giant resonances

The finite amplitude method (FAM) is a very efficient approach for solving the fully self-consistent random-phase approximation (RPA) equations. We use FAM to rederive the RPA matrices for Skyrme functionals, calculate the electric dipole ( E 1) and the magnetic dipole ( M 1) giant resonances, and compare the results with available experimental and evaluated data. For the E 1 transitions in heavy nuclei, the calculations reproduce well the resonance energy of the photoabsorption cross sections. In the case of M 1 transitions, we show that the residual interaction does not affect the transition strength of double-magic nuclei, which suggests that the spin terms in the Skyrme force currently neglected in the present computation could improve the agreement between FAM and experimental data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Hyperfine transitions in He-like ions as a tool for nuclear-spin-dependent parity-nonconservation studies

In this paper a scheme is proposed for measuring nuclear-spin-dependent parity-nonconservation effects in highly charged ions. The idea is to employ circularly polarized laser light for inducing the transition between the level (1s2s){sup 1}S{sub 0} and the hyperfine sublevels of (1s2s){sup 3}S{sub 1} in He-like ions with nonzero nuclear spin. We argue that an interference between the allowed magnetic dipole M1 and the parity-violating electric dipole E1 decay channel leads to an observable asymmetry of order 10{sup -7} in the transition cross section, in the atomic range 28{<=}Z{<=}35. Experimental requirements for asymmetry measurements are discussed in the case of He-like {sub 34}{sup 77}Se.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Approximately 2400-Year Cycle in the Concentration of Cosmogenic Radionuclides: Sources of Variations

Cosmogenic isotopes, including {sup 14}C, {sup 10}Be, and {sup 7}Be, are produced in the Earth’s atmosphere under the effect of cosmic rays. The rate of their production is determined by several factors, such as the intensity of primary galactic cosmic rays, the level of solar activity, and the strength of the Earth’s magnetic field. Changes in the isotope concentrations and distributions receive contributions from mixing processes proceeding in the surrounding medium: the atmosphere, biosphere, and oceans. The isotopes {sup 14}C and {sup 10}Be are the most important for studying solar activity and climate. Investigation of isotope concentrations reveal that there are both long-term trends and cyclic components. As for {sup 14}C, the long-term component caused by the change in the magnetic dipole moment of the Earth with a characteristic time of about 10{sup 4} years is the most commonly known. It is well known that the concentrations of cosmogenic isotopes change cyclically with time. The ~2400-year cycle (Hallstatt cycle) and the ~210-year cycle (de Vries cycle) are the most famous. In the present article, we discuss the possible origin of the ~2400-year cycle.

58 GEOSCIENCES↗
DOE OSTI2011

Noncommutative magnetic moment of charged particles

It has been argued that in noncommutative field theories, the sizes of physical objects cannot be taken smaller than an ''elementary length'' related to noncommutativity parameters. By gauge covariantly extending field equations of noncommutative U(1){sub *} theory to cover the presence of external sources, we find electric and magnetic fields produced by an extended static charge. We find that such a charge, apart from being an ordinary electric monopole, is also a magnetic dipole. By writing off the existing experimental clearance in the value of the lepton magnetic moments for the present effect, we get the bound on noncommutativity at the level of 10{sup 4} TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

INFLATION OF A DIPOLE FIELD IN LABORATORY EXPERIMENTS: TOWARD AN UNDERSTANDING OF MAGNETODISK FORMATION IN THE MAGNETOSPHERE OF A HOT JUPITER

Giant exoplanets at close orbits, or so-called hot Jupiters, are supposed to have an intensive escape of upper atmospheric material heated and ionized by the radiation of a host star. An interaction between outflowing atmospheric plasma and the intrinsic planetary magnetic dipole field leads to the formation of a crucial feature of a hot Jupiter's magnetosphere-an equatorial current-carrying magnetodisk. The presence of a magnetodisk has been shown to influence the topology of a hot Jupiter's magnetosphere and to change a standoff distance of the magnetopause. In this paper, the basic features of the formation of a hot Jupiter's magnetodisk are studied by means of a laboratory experiment. A localized central source produces plasma that expands outward from the surface of the dipole and inflates the magnetic field. The observed structure of magnetic fields, electric currents, and plasma density indicates the formation of a relatively thin current disk extending beyond the Alfvenic point. At the edge of the current disk, an induced magnetic field was found to be several times larger than the field of the initial dipole.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Dynamics of Coronal Hole Boundaries

Remote and in situ observations strongly imply that the slow solar wind consists of plasma from the hot, closed-field corona that is released onto open magnetic field lines. The Separatrix Web theory for the slow wind proposes that photospheric motions at the scale of supergranules are responsible for generating dynamics at coronal-hole boundaries, which result in the closed plasma release. We use three-dimensional magnetohydrodynamic simulations to determine the effect of photospheric flows on the open and closed magnetic flux of a model corona with a dipole magnetic field and an isothermal solar wind. A rotational surface motion is used to approximate photospheric supergranular driving and is applied at the boundary between the coronal hole and helmet streamer. The resulting dynamics consist primarily of prolific and efficient interchange reconnection between open and closed flux. The magnetic flux near the coronal-hole boundary experiences multiple interchange events, with some flux interchanging over 50 times in one day. Additionally, we find that the interchange reconnection occurs all along the coronal-hole boundary and even produces a lasting change in magnetic-field connectivity in regions that were not driven by the applied motions. Our results show that these dynamics should be ubiquitous in the Sun and heliosphere. We discuss the implications of our simulations for understanding the observed properties of the slow solar wind, with particular focus on the global-scale consequences of interchange reconnection.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE COSMIC-RAY INTENSITY NEAR THE ARCHEAN EARTH

We employ three-dimensional state-of-the-art magnetohydrodynamic models of the early solar wind and heliosphere and a two-dimensional model for cosmic-ray transport to investigate the cosmic-ray spectrum and flux near the Archean Earth. We assess how sensitive the cosmic-ray spectrum is to changes in the sunspot placement and magnetic field strength, the large-scale dipole magnetic field strength, the wind ram pressure, and the Sun's rotation period. Overall, our results confirm earlier work that suggested the Archean Earth would have experienced a greatly reduced cosmic-ray flux than is the case today. The cosmic-ray reduction for the early Sun is mainly due to the shorter solar rotation period and tighter winding of the Parker spiral, and to the different surface distribution of the more active solar magnetic field. These effects lead to a global reduction of the cosmic-ray flux at 1 AU by up to two orders of magnitude or more. Variations in the sunspot magnetic field have more effect on the flux than variations in the dipole field component. The wind ram pressure affects the cosmic-ray flux through its influence on the size of the heliosphere via the pressure balance with the ambient interstellar medium. Variations in the interstellar medium pressure experienced by the solar system in orbit through the Galaxy could lead to order of magnitude changes in the cosmic-ray flux at Earth on timescales of a few million years.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

PERIODIC RADIO EMISSION FROM THE M7 DWARF 2MASS J13142039+1320011: IMPLICATIONS FOR THE MAGNETIC FIELD TOPOLOGY

We present multi-epoch radio and optical observations of the M7 dwarf 2MASS J13142039+1320011. We detect a {approx}1 mJy source at 1.43, 4.86, 8.46, and 22.5 GHz, making it the most luminous radio emission over the widest frequency range detected from an ultracool dwarf to date. A 10 hr Very Large Array observation reveals that the radio emission varies sinusoidally with a period of 3.89 {+-} 0.05 hr, and an amplitude of {approx}30% at 4.86 GHz and {approx}20% at 8.46 GHz. The periodicity is also seen in circular polarization, where at 4.86 GHz the polarization reverses helicity from left- to right-handed in phase with the total intensity. An archival detection in the Faint Images of the Radio Sky at Twenty Centimeters survey indicates that the radio emission has been stable for at least a decade. We also detect periodic photometric variability in several optical filters with a period of 3.79 hr and measure a rotation velocity of vsin i = 45 {+-} 5 km s{sup -1}, in good agreement with the radio and optical periods. The subtle difference in radio and optical periods may be due to differential rotation, with {Delta}{Omega} {approx} 1 rad day{sup -1} between the equation and poles. The period and rotation velocity allow us to place a lower limit on the radius of the source of {approx}> 0.13R{sub sun}, about 30% larger than theoretical expectations. The properties of the radio emission can be explained with a simple model of a magnetic dipole misaligned relative to the stellar rotation axis, with the sinusoidal variations and helicity reversal due to the rotation of the magnetic poles relative to our line of sight. The long-term stability of the radio emission indicates that the magnetic field (and hence the dynamo) is stable on a much longer timescale than the convective turnover time of {approx}0.2 yr. If the radio emission is due to gyrosynchrotron emission the inferred magnetic field strength is {approx}0.1 kG, while the electron cyclotron maser process requires a field of at least 8 kG.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Conceptual Design of a 20 T Hybrid Cos-Theta Di- pole Superconducting Magnet for Future High-Energy Particle Accelerators

High energy physics research will need more and more powerful circular accelerators in the next decades. It is therefore desirable to have dipole magnets able to produce the largest possible magnetic field, in order to keep the machine diameter within a reasonable size. A 20 T dipole is considered a desired achievement since it would allow the construction of an 80 km machine, able to circulate 100 TeV proton beams. In order to reach 20 T, a hybrid Low-Temperature Superconductor (LTS) - High-Temperature Superconductor (HTS) magnet is needed, since LTS technology is presently limited to ~16 T for accelerator magnet applications. In this paper, we present the design of a 6 layers 20 T hybrid dipole magnet using Nb3Sn (LTS) and Bi2212 (HTS). We show that it is possible to achieve this magnetic field with accelerator field quality, with sufficient margin on a realistic conductor, keeping the stresses within safe limit, avoiding conductor degradation

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Gyrokinetic particle simulation of drift-compressional modes in dipole geometry

Gyrokinetic particle simulation of low frequency compressional modes has been developed using flux coordinates in the global magnetic dipole geometry. The compressional component is formulated in a scalar form of the parallel magnetic perturbation, and the gyro-averaging is performed explicitly in the configuration space. A reduced gyrokinetic model, in which the compressional perturbations are decoupled from the shear Alfven and electrostatic perturbations, has been implemented. Linear simulation results have been verified using a numerical Nyquist analysis of the dispersion relation in the slab limit. Global simulations of unstable drift-compressional modes in the dipole geometry with kinetic ions find that finite Larmor radius (FLR) effects reduce the linear growth rate significantly but change little the real frequency. Global eigenmode structures show that the modes are even along the equilibrium magnetic field and broadened by the FLR effects in the radial direction. Radial propagation away from the region of excitation is observed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Linearized kinetic theory of spin-1/2 particles in magnetized plasmas

We have considered linear kinetic theory, including the electron-spin properties in a magnetized plasma. The starting point is a mean-field Vlasov-like equation, derived from a fully quantum-mechanical treatment, where effects from the electron-spin precession and the magnetic dipole force are taken into account. The general conductivity tensor is derived, including both the free current contribution and the magnetization current associated with the spin contribution. We conclude the paper with an extensive discussion of the quantum-mechanical boundary where we list parameter conditions that must be satisfied for various quantum effects to be influential.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

A quantum liquid of magnetic octupoles on the pyrochlore lattice

Spin liquids are highly correlated yet disordered states formed by the entanglement of magnetic dipoles. Theories define such states using gauge fields and deconfined quasiparticle excitations that emerge from a local constraint governing the ground state of a frustrated magnet. For example, the ‘2-in–2-out’ ice rule for dipole moments on a tetrahedron can lead to a quantum spin ice in rare-earth pyrochlores. However, $f$-electron ions often carry multipole degrees of freedom of higher rank than dipoles, leading to intriguing behaviours and ‘hidden’ orders. In this paper we show that the correlated ground state of a Ce 3+ -based pyrochlore, Ce 2 Sn 2 O 7 , is a quantum liquid of magnetic octupoles. Our neutron scattering results are consistent with a fluid-like state where degrees of freedom have a more complex magnetization density than that of magnetic dipoles. The nature and strength of the octupole–octupole couplings, together with the existence of a continuum of excitations attributed to spinons, provides further evidence for a quantum ice of octupoles governed by a ‘2-plus–2-minus’ rule. Our work identifies Ce 2 Sn 2 O 7 as a unique example of frustrated multipoles forming a ‘hidden’ topological order, thus generalizing observations on quantum spin liquids to multipolar phases that can support novel types of emergent fields and excitations.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Suppression of the quantum-mechanical collapse by repulsive interactions in a quantum gas

The quantum-mechanical collapse (alias fall onto the center of particles attracted by potential -r{sup -2}) is a well-known issue in quantum theory. It is closely related to the quantum anomaly, i.e., breaking of the scaling invariance of the respective Hamiltonian by quantization. We demonstrate that the mean-field repulsive nonlinearity prevents the collapse and thus puts forward a solution to the quantum-anomaly problem that differs from that previously developed in the framework of the linear quantum-field theory. This solution may be realized in the 3D or 2D gas of dipolar bosons attracted by a central charge and in the 2D gas of magnetic dipoles attracted by a current filament. In the 3D setting, the dipole-dipole interactions are also taken into regard, in the mean-field approximation, resulting in a redefinition of the scattering length which accounts for the contact repulsion between the bosons. In lieu of the collapse, the cubic nonlinearity creates a 3D ground state (GS), which does not exist in the respective linear Schroedinger equation. The addition of the harmonic trap gives rise to a tristability, in the case when the Schroedinger equation still does not lead to the collapse. In the 2D setting, the cubic nonlinearity is not strong enough to prevent the collapse; however, the quintic term does it, creating the GS, as well as its counterparts carrying the angular momentum (vorticity). Counterintuitively, such self-trapped 2D modes exist even in the case of a weakly repulsive potential r{sup -2}. The 2D vortical modes avoid the phase singularity at the pivot (r=0) by having the amplitude diverging at r{yields}0 instead of the usual situation with the amplitude of the vortical mode vanishing at r{yields}0 (the norm of the mode converges despite of the singularity of the amplitude at r{yields}0). In the presence of the harmonic trap, the 2D quintic model with a weakly repulsive central potential r{sup -2} gives rise to three confined modes, the middle one being unstable, spontaneously developing into a breather. In both the 3D and 2D cases, the GS wave functions are found in a numerical form and in the form of an analytical approximation, which is asymptotically exact in the limit of the large norm.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗